NFL

FOOTBALL & COACHING IN BLOOD FOR RYANS

Occasionally in the defensive film room, Rex Ryan will grow more animated than usual.

The Jets coach will give a spirited introduction to the next clip.

“This is how we need to play defense,” he’ll tell the players. “If we play defense the way this guy did, we’re going to play ball.”

Then he will press play and a clip of a youth league football game will be on the screen. As the players watch a diminutive defensive back make an interception, they will laugh as they realize Coach Ryan just became Proud Papa Ryan. The defensive star on the screen is his teenage son, Seth.

“He’s a proud dad,” said linebacker Bart Scott, who played for Ryan in Baltimore and followed him to the Jets.

Today, Ryan will take a break from plotting how to rattle Tom Brady or shut down the Dolphins and spend Father’s Day with his two sons — Payton, 16, and Seth, 15.

New York fans already have seen how enthusiastic Ryan can be when talking about football. Mention his sons and the enthusiasm grows higher. The 46-year-old rookie head coach will tell you about how good Payton is at karate or how smart he is. He will tell you about Seth’s latest baseball tournament and about his charisma.

In the Ryan household, football is more than a sport, it’s the family

business. Rex’s father, Buddy, spent nearly 30 years in the NFL as an assistant and head coach. Rex’s twin brother, Rob, is the defensive coordinator for the Browns. And Seth might be the next branch on the coaching family tree.

“I would love to coach,” Seth said. “I’d be a third-generation coach. That’s all I really want to do. Just seeing my dad out there, I want to be like him someday.”

He already has begun his education. Seth was a constant presence around the Ravens, hanging around practices and running end-zone-camera photos to the coaches on the sideline game day.

Buddy Ryan tried to talk Rex and Rob out of coaching.

“It’s a tough-ass business,” the 75-year-old patriarch of the family said. If Seth wants a life on the sideline, though, Rex would give his blessing.

“Look at my family, football has been fantastic for us,” Rex said. “This is our livelihood. It’s the family business. I’m not discouraging them from it. I know it’s a great way of life.”

Rex knows what it’s like to grow up around the game. His parents were divorced when he was 3 and he and his two brothers lived with his mother in Toronto. Still, they visited their father when he became an assistant with the Jets in 1968 and were at Super Bowl III in Miami.

In 1977, when Rex was 14, he went to live with his father, then in Minnesota as an assistant for the Vikings. After one year there, they moved to Chicago when Buddy became the defensive coordinator of the Bears. Rex and Rob served as ball boys for the Bears, soaking it all in.

“It was awesome,” Rex said. “We were learning all the time. I was a huge fan and I knew the game. I think what it did for me was . . . I’m not intimated by anybody. I was hanging around Walter Payton. I mean, it’s not like anyone will intimidate me. I don’t care who I meet.”

Rex so adored Payton, the legendary late running back, that he named his first son after him.

After playing at Southwestern Oklahoma State, Rex and Rob wanted to coach. Buddy tried to talk them into a more stable career, but eventually relented and gave them a crash course in his famed “46 defense.”

Rex and his wife, Michelle, were married in 1987. She knew nothing about football when she met him but soon figured out what the game meant to him.

“Rex has a love of the game of football,” she said. “It’s not just a career. There’s a genuine love of football. There was never any question in his mind of what he wanted to do.”

After bouncing around the college ranks as an assistant, Rex joined Buddy’s staff with the Arizona Cardinals in 1994. The cries of nepotism made Rex work that much harder. He missed Seth’s birth because he did not want to leave an offseason practice.

When Rex became an assistant in Baltimore in 1999, his sons were old enough to bring around to practice. Payton liked the game, but did not fall in love with it. He reminded Rex of his older brother Jim, who is a lawyer in St. Louis. Seth, on the other hand, couldn’t get enough.

Some days, Rex would be ready to go home from the practice facility but couldn’t find Seth. Soon, he would discover him chatting up general manager Ozzie Newsome or fooling around with defensive back Samari Rolle.

“Some people dream to meet [the players],” Seth said. “I get a chance to talk to them, play catch, run drills with them.”

Seth made his Jets debut in April at a minicamp. He lined up as a receiver during defensive drills with Rex throwing him passes.

“He was our third-down back,” Scott said. “Rex would consistently set him up with crossing routes and throw a nice lofted pass to

toughen him up a little bit.”

Being the coach’s son does have some downsides. Michelle worries about the heckling her sons will take, especially now that Rex is a head coach. Payton is going to finish high school in Maryland, but Seth is moving to New Jersey and probably will hear it when the Jets stumble.

When Seth plays football, he feels the expectations people have of him because of his bloodlines — not that it bothers him.

“People do expect me to be some superstar athlete but I don’t expect anything less of myself,” Seth said. “I expect to be out there tearing up the field. If I have a bad game I feel bad, but if my team wins I’m still thrilled.”

Seth is preparing to go to training camp with his dad next month in Cortland, N.Y. He will not be there just to have fun. He also will be learning, preparing to be the next Ryan coach, watching his role model.

“My dad has done a great job and I’d try to be just like him,” Seth said.

He already is on his way. When asked about how he thinks the Jets will do this year Seth said,

“I think we’re going to be competitors to go to the Super Bowl.”

Yep, he’s a Ryan.

brian.costello@nypost.com