PITTSFORD, N.Y. -- Before we can begin, Rex and Rob Ryan must finish their nature walk. It involves five middle-aged men, all Buffalo Bills staffers, and lasts about half an hour. Rex organized the daily jaunt because he says he has gained 30 pounds since his brother joined the coaching staff this past winter. The walk twists around the picturesque campus of St. John Fisher College, home of the Bills' training camp, and ends on a long flight of concrete steps.

Good god, it's a sight to behold -- Rob's long gray mane bouncing in the wind, Rex trash-talking the whole group. In a way, it's depressing because, in the old days when the twin brothers were together, they sprinted, drank copious amounts of beer and raised hell.

Now, their precious leisure time is relegated to what they call the "Huck Finn walk." When they clear those last steps, creaky bones be damned, they throw their arms in the air, Rocky style.

"I'm down a pound!" someone in the group exclaims after a weigh-in.

"I'm up 13!" says Bills staffer Ernie Gutierrez, who, according to Rex, really enjoys camp food.

Rob Ryan, at least initially, was not as passionate about this whole health kick. Back in December, a month before he was hired, Rob visited Buffalo with one of the Ryans' childhood friends, Chuck Abate. Rex is really into salads, and he insisted that they join him for his daily lettuce lunches. Rob and Chuck reluctantly agreed, but then sneaked over to the team cafeteria and scarfed down a premeal meal before they met Rex.

"You guys," Rex told them midsalad, "are doing so good."

The Ryan boys are back together for the first time since Arizona more than two decades ago, and it's going to be entertaining. They coach hard, cackle long and then retreat to Rex's office late at night and watch "Naked and Afraid." Their defensive meetings are already getting rave reviews. In most NFL training camps, these meetings, wedged between hot workouts, should be sponsored by Ambien. But not Rex and Rob's. Rex goes to the front first, talks a bit, then motions for a relief pitcher. The song "Wild Thing" cranks, and Rob struts to the dais, in sort of a WWE walkup, and high-fives players along the way. Nobody sleeps.

They don't talk about it or act like it, but this is the most important football season in the history of the Ryan family. Rob could be found sleeping in his office this spring -- months before the first game -- because he has to get everything right. They have to get it right. Rob is coming off a forgettable year in New Orleans in which the defense put up historically bad numbers, and he was fired; Rex came to Buffalo in 2015 promising the playoffs, only to see his team regress and go 8-8.

The Bills have not seen the postseason in 16 years, and the pressure is mounting. In June, Hall of Famer Jim Kelly told "The Jim Rome Show" that if Rex's team didn't make the postseason this year, he probably would be fired.

So when a city doubts you and livelihoods are on the line, it's only natural to turn to the person you trust the most, the one who has been part of you for 53 years. Rob watched his brother's team for a week last winter and was struck by the way the Bills, after months of discord, were coming together. He wanted to be part of it.

But something bigger was at play, too. The twins got into coaching because of their father, Buddy, and he was struggling. You name it, and Buddy had it -- congestive heart failure, cancer, Parkinson's disease and numerous strokes. They knew that he wasn't going to be around much longer, and that their success together would give him great joy.

The legendary defensive coach rallied many times, to the point where his doctor stopped saying "Call the boys" every time things looked bad. He had one big reason to live. He wanted to be in Buffalo on Sept. 15, the Bills' home opener against the Jets.

"My boys are together," he'd tell anyone who'd listen. "My boys are going to kick ass."

But then Buddy died on June 28, and now everything seems different. If it's August, it usually means a Ryan is boasting about his team's Super Bowl aspirations. Buddy did it for years, and so have his sons. But now there are no predictions, just one inevitability.

"We had the courage to coach together knowing if it doesn't succeed, who's the blame going to?" Rex says. "The blame is going to be saddled onto two people for an entire organization."

"That's fine," Rob says. They know when they're together, they rarely lose a fight.

FROM THE VERY beginning, Buddy Ryan told his children to never, ever, get into coaching. For one, there was no money in it back in his day. Buddy's first NFL job was as a defensive line coach for the New York Jets, a gig that won him a Super Bowl ring but could barely afford him a room at the YMCA. Imagine this, Buddy Ryan, a hard, calculating man once accused of putting bounties on opponents, sleeping in a one-bed room at the Y, his three visiting sons cuddled next to him. That's how glamorous it was to be a coach.

But after Buddy told his kids not to do it, only one of them listened. The oldest.

It's late July, a few weeks after Buddy's death, and Jim Ryan is sipping cabernet at a cocktail lounge on the outskirts of St. Louis, anonymous in a happy hour sea of suits. Jim is a lawyer, and he's in the middle of a murder trial. He has the most normal job in the family.

Six years separate Jim from Rex and Rob, so Jim was old enough to know what football did to his parents' marriage.

"Here was my childhood," Jim says. "I was born in Oklahoma; my dad wasn't around because he was busy. Kindergarten through second grade, I was in Buffalo, New York, third grade in Nashville, fourth and fifth in Ardmore, Oklahoma, and sixth grade in Toronto. Between marriages falling apart and moving with the jobs, it's a tough living."

Buddy and Doris Ryan were college sweethearts, two strong-willed Oklahomans who grew apart and got divorced after 11 years. Doris couldn't be one of those wives stuck at home waiting a season to see her husband. She took the three kids to Toronto and became Canada's first female education administrator.

Jim knows he's more like his mom. He reads books and prefers hockey to football. He does not have the capacity to be as blunt as Buddy.

True story: Jim walked on to play hockey at the University of Minnesota and for a short time played under Herb Brooks. One day, Brooks cut him. Now, hockey parents are known for being occasionally biased and intrusive, and Buddy had a long track record of standing up for his boys. But when Jim told his dad he had been cut, Buddy simply said, "That just goes to show that he knows talent."

But that's the reality of being a Ryan. You're born with extra-thick skin. By the time Rex and Rob were in second grade, they knew they wanted to be coaches, just like their dad. Around that same time, Jim also knew they'd be trouble.

School was always secondary to them. Jim estimates that they have read one nonsports book combined. If one twin had a test and didn't know the subject, the other would take it and the teacher would never catch on.

"They were just a handful," Jim says. "And they always had each other. When you're a little kid, you kind of feel alone. It's natural. They never had that feeling. And God [help] the kid that crossed them."

Because of fights, and a few general mishaps, Rob was constantly suffering broken bones. One time, when he broke his arm, Rex and Jim shoved cheese and bologna down his cast. They wondered how it would smell after a few weeks.

"I remember my grandma, I think, took him to take the cast off," Jim says. "The doctor about passed out, and the nurse had to leave because she was gonna puke."

Fights were often lopsided because if you picked on one Ryan brother, the other came out swinging, too. When the twins were in their early teens, Doris, tired of juggling work and two rowdy sons who were constantly getting into fights, decided to let them live with their father. Buddy was an assistant with the Minnesota Vikings at the time, coaching the Purple People Eaters defense in 1976 and '77, and lived in the Minneapolis suburb of Edina. The twins thought Edina was too snobby.

But in the NFL, the only guarantee is change, and in 1978, the Chicago Bears hired Buddy to be their defensive coordinator. Rex and Rob arrived in Chicago after the high school baseball season had started, so the team at Stevenson High was already set. But then Buddy walked in and handed the baseball coach a business card with a Bears helmet on it, and soon the twins were on the team.

Chuck Abate, who played second base, was irritated when the Ryans showed up. He thought they were getting preferential treatment because their dad was a coach.

"I wanted to hate those guys so much," Abate says. "I hated them for about one day, but ended up loving them for the rest of my life. I think I was jealous of them. They were so tight. They didn't care. They had each other."

The brothers, born five minutes apart, were so tight they shared a car and a wallet. Since Rex was born first and was technically older, he always drove the red Ford Escort.

When they were around 16, they were ball boys for the Bears. One day, the twins asked Bears defensive tackle Dan Hampton, a future Hall of Famer, whether he'd buy them a six-pack of beer.

"What the hell's wrong with you?" Hampton said.

Buddy helped nudge them toward college, and they played a little football and wreaked a lot of havoc at Southwestern Oklahoma State. But that was where Buddy's involvement ended. He did not want to be the guy who handed his boys jobs on silver platters. He knew if things went bad, it meant all of them would be gone. "One bullet gets both of you," is something he liked to say about nepotism.

So Rex went to Eastern Kentucky to be a grad assistant, Rob went to Western Kentucky to be a G.A., and, in one of the rare times of their young lives, the twins were apart.

EVERYBODY KNOWS what happened to Rex. He became head coach of the New York Jets in 2009, led them to two straight AFC Championship Games, and dazzled the NFL with his wit and brash talk. When Rex said he wouldn't kiss Bill Belichick's rings, it brought back memories of Buddy. Rex has been in the spotlight ever since.

But a monumental thing happened before all of that, and it's something that changed Rex's and Rob's lives. In 1994, the year after their dad punched fellow Oilers assistant Kevin Gilbride on the sidelines, the Arizona Cardinals made Buddy Ryan their head coach in what would be his last NFL job.

Buddy's sons were toiling away at the small-college level at the time and could not get a sniff from anyone bigger. The Division I-A coaches tended to look down on the guys in the lower levels, Rex says, and then there was that matter of the punch.

When Buddy clocked Gilbride -- in a "Sunday Night Football" game, no less -- Rex and Rob were frantically calling each other. Rex says they cried: "We're never, ever going to get a coaching job!"

There are varying accounts of why Buddy decided to go to Arizona. Some people insist that he took the job because he knew it might be the only way his boys would have a chance to get into the NFL. Jim, who was Buddy's agent at the time, says that his dad was actually against hiring them and that, even when Jim got him to reconsider, Buddy was going to take only one of them.

When told of Jim's account, that only one of them was supposed to be hired, Rob laughs.

"Which one?" he says.

"It almost hurt being Buddy Ryan's son," Rex says. "You would think that it would help, but it really didn't. If Dad wasn't going to hire us, who would?"

He took both of them. Rex coached the defensive line and linebackers, and Rob ran the secondary. In Rob's first day on the job, Jim says, Rob had to cut Dave Duerson, a safety whom Buddy had coached in Chicago.

Duerson was getting older and wanted to play another year, but Buddy told Rob that if Duerson couldn't run a 4.6, they couldn't keep him. Duerson couldn't run a 4.6.

Though Rob was only 31, he immediately won over the players. Cornerback Aeneas Williams didn't want to play for Buddy in 1994 because Williams was sure he couldn't stand up to the demands of Buddy's system, which would require him to be on an island.

One of the first people Williams saw was Rob, who put his arms around him. "Aeneas," Rob told him, "you can lead this league in interceptions, you can be an All-Pro corner, and you can make the Pro Bowl."

Williams was inspired. He tied for most interceptions in the NFL in 1994 and went on to the Pro Football Hall of Fame.

The Cardinals finished 8-8, their first .500 campaign since moving to Phoenix in 1988, and took their playoff hopes all the way to the final game of the year. But they went 4-12 in '95, and Buddy, who was notorious for clashing with ownership, was fired.

And that was it for Buddy. He was content to go home to his farm in Kentucky and wear two hats on weekends, one for Rex's team and one for Rob's.

Rob went back to college coaching; he was the defensive coordinator at Oklahoma State when Belichick hired him in 2000 to be the Patriots' linebackers coach. They won two Super Bowls together. In the past decade, Rob has been the defensive coordinator for four NFL teams -- Oakland, Cleveland, Dallas and New Orleans -- but has yet to be a head coach.

His supporters aren't exactly sure why. If Rob had been from another era, one that was less image conscious, maybe he would've had a better shot. Maybe if he'd cut his hair, or held his tongue once in a while, he'd be where Rex is now.

But that wasn't Rob's way. He is more like Buddy. He has no filter. Rex, for all of his bravado, is still polished. He knows when to dial it down.

The Bills announced Rob's hiring on Jan. 10, and he went dark for months. But in May, he did an interview with The MMQB and let loose. He told the website that the Saints struggled in his final two seasons because he was forced to change their scheme against his wishes. He said they switched to a "bulls--- defense" to try to copy the Seattle Seahawks. (New Orleans coach Sean Payton later disputed Rob's claim that his stamp wasn't on the defense.)

The Saints were fourth best in yards allowed in Rob's first season in 2013, but were abysmal in his the final two years.

"I think we would've been better [in Oakland] if Al Davis wasn't micromanaging everything," former defensive back Chris Carr says.

"Same thing in New Orleans [with] Sean Payton," says Carr, who played under Ryan for both teams. "If he's in a situation where he has a head coach like his brother that knows him and is going to believe in him and let him do his thing, I think he's going to perform well."

The Ryans are vague when asked what type of defense the Bills will run this season, saying only that it will be "multiple." When it's run right, Rex says, it's organized chaos. They know what they're doing, but they're putting a doubt in the offense's mind.

One of Rex's only gripes about camp with his brother is that he can't go out because everyone recognizes Rob with his hair. Some nights, Rob pops into Rex's office, and they'll watch "Naked and Afraid" or "Deadliest Catch." The latter features a family of fishermen who run a ship on the Bering Sea.

"Hopefully one day Edgar's running his boat," Rex says, "and Rob's running his ship."