Nick Bosa is a soft-spoken defensive end with perpetual stubble who was drafted No. 2 overall from Ohio State. Bosa made an immediate splash in the NFL, earning Rookie of the Year honors and quickly helping the 49ers return to relevance.

Jake Kumerow is a gregarious wide receiver with a thick, scraggly beard. Kumerow, undrafted from Division III Wisconsin-Whitewater, spent three long seasons on practice squads and injured reserve before finally reaching the field with Green Bay.

And now these cousins, sharp contrasts and all, will meet in Sunday’s NFC Championship Game.

Bosa and Kumerow formed a strong bond in 2015, as Kumerow prepared for his pro career. He lived with Bosa and his mom, Cheryl, for eight weeks in Fort Lauderdale, Fla. — Cheryl’s brother, Eric Kumerow, is Jake’s dad — and diligently trained in hopes of landing in the NFL.

Bosa was still in high school at the time, and he and his cousin fell into a routine. Jake left every morning to train at the same time Nick went to school … Jake returned in late afternoon and headed outside to fish on the river (part of the Intracoastal Waterway) behind the house … and Nick, once done with his after-school training, joined him for fishing, dinner and time in the hot tub.

“Jake is a really good influence on my boys,” Cheryl Bosa said. “He doesn’t like sitting around. He’s always saying, ‘Let’s go rent a boat, let’s go here, let’s go there.’”

Nick and older brother Joey Bosa, now a two-time Pro Bowl defensive end with the Chargers, always were self-motivated. They also blossomed into big-name players at Ohio State; Joey Bosa was a similarly high draft choice, going No. 3 overall in 2016.

So watching the persistence and tenacity of their cousin — which Kumerow needed simply to make the NFL — provided some perspective.

“I got to see how hard Jake had to work to get to where he was, and how many tough years there were on the practice squad and stuff like that,” Nick Bosa said this week. “He’s earned everything he’s got. I’m proud of him.”

Jake Kumerow counts as the unsung member of an accomplished football family. His dad was a first-round draft choice (No. 16 overall) of the Miami Dolphins in 1988, another decorated defensive end from Ohio State.

Eric Kumerow soon became good friends with yet another defensive end, from Boston College, taken No. 16 overall the previous year: John Bosa. Kumerow introduced his sister Cheryl to Bosa, and they subsequently got married and had Joey and Nick. (The Bosas have since divorced.)

John Bosa and Eric Kumerow both saw their NFL careers cut short by injuries. All these years later, they’re savoring the chance to watch their sons chase quarterbacks or catch passes at the game’s highest level.

“We never imagined what these kids would do,” Eric said.

Jake Kumerow spent most of 2015, ’16 and ’17 alternately signing with and getting waived by Cincinnati. He also spent two weeks on New England’s practice squad before he joined the Packers in December 2017.

This was a good match geographically, given his college success in Whitewater — the Warhawks won two national championships during Kumerow’s three seasons at the school. (He originally walked on at Illinois before transferring.) It also turned out to be a welcome chance to play, as Kumerow found his niche as a reserve receiver and special teams standout in Green Bay.

He caught eight passes last season and 12 more this season, including a 37-yard, tiptoe-along-the-sideline touchdown grab Oct. 20 against the Raiders. That play inspired some Packers fans to dub Kumerow “Cheese Jesus,” a nod to his distinctive facial hair.

More often, he happily toils in anonymity. Kumerow excels as a blocker, as he showed on Aaron Jones’ 1-yard touchdown run last Sunday against Seattle. Kumerow kept Seahawks defensive end Jadeveon Clowney from making the play.

“He’s been able to hang in there for five years,” Eric Kumerow said of his son. “I don’t think he’s ever thought about giving it up. He loves to play — it’s the one thing he’s been certain he wanted to do his whole life. He’s wanted to pursue this thing to the end.”

Jake Kumerow declined The Chronicle’s interview request, though he did speak to a small group of reporters Thursday in Green Bay. Asked about Nick Bosa being named Rookie of the Year earlier this week, Kumerow said, “It’s my little cousin, so I’m real happy for him. I’m glad he got that honor.”

Kumerow, now 27, and Bosa, 22, didn’t spend much time together growing up, because the Kumerows moved from South Florida to suburban Chicago in 2003. But they connected at occasional family get-togethers, and then grew closer during Kumerow’s draft preparations.

They swapped jerseys Nov. 24 in Santa Clara, after the 49ers rolled to victory over the Packers, and now they return to Levi’s Stadium with more at stake: the NFC title, a Super Bowl berth and family bragging rights. There will be a strong Bosa/Kumerow presence in the crowd Sunday, an uncommon mix of 49ers and Packers jerseys mingled together.

Meantime, back home in Florida, 80-year-old Marie Kumerow — grandmother to both Jake and Nick Bosa — will watch with great interest.

“She’s just blown away by all this,” Eric Kumerow said of his mom. “When she wakes up Monday morning, one of her grandchildren is going to be playing in the Super Bowl. She’s guaranteed a trip to the Super Bowl.”

Ron Kroichick is a San Francisco Chronicle staff writer. Email: rkroichick@sfchronicle.com Twitter: @ronkroichick