Brad Arthur once sought advice from Ivan Cleary on how to coach his son, now he and Jake are trying to join the Clearys as father-son NRL premiership winners.

Before a ball is even kicked on Sunday, the Clearys and the Arthurs will already have made history.

Together, they will become the first father-son and coach-player combinations to front up against each other in an NRL decider.

Come fulltime, one pair will walk away with further history.

A Penrith win will make Ivan and Nathan the first father-son combination in history to win two titles, backing up last year's success.

Alternatively, the Arthurs can join them and John and Martin Lang as the only other premiership-winning combination if the Eels break their drought.

For Nathan and Ivan, working together in big matches has been a regular occurrence.

"It's sort of become the norm now," Nathan said of playing under his father.

"It's probably not something that you really notice until after the year is done and you reflect.

"I'm very grateful that I'm in this position. It's unique. Just very grateful.

"When it's all said and done and we're probably both retired we can reflect on what it was.

"But at the moment it's just a job."

For Brad and Jake, it's a new phenomenon.

"I'm excited and I'm excited for him," coach Arthur said.

"But I'm sure Ivan's the same. I feel like we've got 17 sons. We're going into this weekend with 17 priorities.

"It's about these guys being a bit more selfish now and playing for themselves. They've put themselves in this position."

Fathers coaching their sons in the NRL is rare before even considering grand finals.

There remain only 12 such instances in the game's 114-year history, while John and Jasmin Strange became the first father-daughter combination in the NRLW this year at the Sydney Roosters.

But the Clearys have long been seen as the leaders in the father-son coaching space in recent years.

After Ivan admitted he faced some challenges in their early days together in 2019, they now hold a 60-18 record together at Penrith.

So much so, that when Brad Arthur went to bring Jake into the Eels' full-time squad last year as playmaking cover, he went straight to Ivan for advice.

"Why wouldn't I reach out for that advice? And to (Ivan and Nathan's) credit, they were excellent," Arthur said.

"It was a tough decision (to bring Jake in).

"I had introduced my son into the team. I consulted with some players as well.

"But I reached out to Ivan and he was great just to give me a bit of advice around it. He'd been there before in terms of coaching his son.

"It's unique. No one ever knows the experience until you actually do it.

"Everyone can say that they they might ... but until you actually do it, you don't know."

Come Sunday night, he and his son could feel something less they know of: winning a premiership.