NEW YORK – It is quickly becoming one of Major League Soccer’s fiercest rivalries, and the #NYDerby even has members of the same family split on which color claims New York City.

Meet the Allen family from Old Bridge, N.J.

On the blue side is RJ Allen, a starting fullback for New York City FC, and on the red side is his younger brother Brandon Allen, a forward trying to break into the New York Red Bulls lineup. The rivals will meet for the third time this season on Sunday at Red Bull Arena (1 pm ET; FOX in the US, TSN5 in Canada).

RJ has played in all five chapters of the #NYDerby, earning his first MLS start in the inaugural clash, assisting on NYCFC's lone goal in a 2-1 loss at Red Bull Arena.

“It was definitely a really special moment for my family and for me as well,” RJ says. “It was a very disappointing end result, but for my first start to come away with an assist like I did, it was a great first game for me. I’m very blessed to be in that situation and to be given the opportunity that I was.”

Brandon has watched the games but has yet to step on the field. He’s hoping that happens sooner rather than later.

“To play in that game must be incredible, the atmosphere, all the fans,” Brandon says. “It must be absolutely incredible.”

Like the fans of both teams, the sibling rivalry between RJ and Brandon ramps up in the week leading up to the #NYDerby.

“Growing up we used to always talk trash, but now that we actually get to play against each other, it’s crazy,” Brandon says. “If I ever get a chance to go at him one-on-one, I’m going to take him on for sure. I’m going to go at his left.”

“When the ball gets dropped and the whistle blows for 90 minutes, it’s my job and my career and anything goes,” adds RJ. “Once the final whistle blows, he’s my brother again.”

RJ's journey to NYCFC

For RJ, it has been a long, arduous journey from professional hopeful to MLS starter. Selected by Chivas USA with the fifth pick of the 2012 MLS Supplemental Draft, Allen never latched on with the club and headed to Denmark to play for Skive IK.

He played 13 matches in the Danish First Division then returned home to New Jersey, coaching the U-10 boys team at Staten Island United while preparing himself for his next pro shot.

“After playing in Denmark, I came home and trained with D.C. United, with Orlando City, with the Cosmos, but I knew I wanted to play in MLS,” he says, adding that he also trained with the Red Bulls. “Unfortunately D.C. didn’t give me an offer, it was one of their bad years. After that I was just coaching to make some money and get by. I was staying fit and waiting for that phone call.”

That phone call came from NYCFC, but it wasn’t exactly the one RJ was hoping for.

The club asked RJ if he would be available to train with David Villa ahead of the club’s inaugural season. Red Bulls midfielder Mike Grella joined them for regular workouts at Ramapo College in northern New Jersey.

When Villa and NYCFC headed to Manchester for the club's inaugural preseason, RJ wasn't on the plane.

Still, he wasn't deterred.

NYCFC got off to a slow start, and there were some injury concerns in the defensive third. RJ’s phone rang again. Then NYCFC head coach Jason Kreis was on the other end.

“It was a call I’ve been waiting for – for a really long time. I knew I had to take advantage of my opportunity when I got that phone call,” RJ says. “I always knew and felt I was good enough to play in this league and to even be a top fullback in the league, but it was just never the right timing or opportunity given to me.”

RJ made his first appearance a few days later on May 3 against the Seattle Sounders. Seven days later, he was in the starting lineup against the Red Bulls. He hasn’t looked back, starting 25 of the 28 matches he’s appeared in as a regular starter for both Kreis and current head coach Patrick Vieira.

“Every time I step on the field," RJ says, "I try to take advantage of every opportunity given to me and to continue to prove to myself and to all the coaches who didn’t want to pick me up early in my career that they made a mistake."

Brandon's waiting game

Brandon Allen is trying to become an MLS starter like his big brother. But the 22-year-old forward knows that won’t be easy with Bradley Wright-Phillips occupying the lone striker role in the Red Bulls' competitive starting XI.

“I look at it as some guys’ opportunity is now and right now it’s just not my time because of the club I chose to go to and the guys who are in my position compared to other people,” Brandon says. “It’s different situations and I completely understand.”

Brandon seemed to be on a direct path to play for the Red Bulls after two sensational seasons in the club's academy, but that path became a bit murkier when he went to Georgetown, where he took summer classes that prevented him from playing for the Red Bulls U-23s for two years.

With the Hoyas, Brandon was one of college soccer’s top strikers, a three-time All-American who scored 50 goals in 91 career games.

He was trying to decide between entering the MLS SuperDraft or going the Homegrown route last winter when he received a call from the Red Bulls.

“They wanted to hear I wanted to be at the club and felt pretty confident about going there,” Brandon says. “They just wanted to hear my side of things, and I said I was very happy and would love to be at the club.”

That was all Red Bulls brass needed to hear. On Dec. 21, Brandon joined Derrick Etienne and Tyler Adams as three of a league-high seven Homegrown signings for 2016.

Brandon has spent much of his rookie season with Red Bulls II in the USL, scoring eight goals in 15 appearances, including a hat trick against FC Montreal on July 9.

He made his MLS debut as a substitute in a 3-0 win against Toronto FC at Red Bull Arena on May 28. For a moment, Brandon thought he had scored his first career MLS goal when he tapped in a Sean Davis cross in the 89th minute, but he was ruled offside.

“As a rookie, you just have to play it by ear and whatever happens happens,” Brandon says. “It’s your first year and you have to understand other people are in front of you. I just have to be patient, keep working hard and my time will come.”

Proud mom

Is New York blue or is New York red?

RJ and Brandon's mother Beatrice and the rest of the family don’t take sides on the three days a year that decide which club – and which Allen brother – will rule the Big Apple soccer scene. Their allegiances are split.

“We’re blessed they’re both so close to home and both playing for two of the best organizations around,” Beatrice says. “They’re both very happy and love the fact they’re playing for their hometown basically. From a parent’s perspective, that’s three games a year you’re supporting both of your kids and not rooting for any particular organization to win. For three days out of the year, it’s not about colors.”

Thanks to Beatrice’s sister, Ann Marie Davis, the family doesn’t have to choose. She created a mashup jersey – half RJ blue and half Brandon red – that will make its debut at Red Bull Arena on Sunday afternoon when the two rivals clash again.

“We have a lot of family and friends coming out to support both of them,” Beatrice says. “I’m sure there’s going to be a tailgate in the morning, a little partying and it’s just going to be great. I hope they both get on the field. It would be a moment we’d all remember.”