Nathan Cleary felt it from the moment he first partnered up with Jarome Luai as a 15-year-old.
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"It just fit," Cleary told AAP.
"It felt like that as soon as Romey and I played together.
"Obviously it has built a lot since then, but I think it was one of those seamless transitions for both of us. We complemented each other really well.
"We both understood the game in the same way and understood we could make each other better."
By Penrith's own admission, Melbourne's spine for Sunday's grand final has more strike and ability to connect from anywhere on the field.
Ryan Papenhuyzen brings the spark, Cameron Munster the off-the-cuff play style, Jahrome Hughes the Dally M form and Harry Grant the smarts.
But in Cleary and Luai, Penrith have one of the greatest halves combinations in rugby league history preparing for their final ride at the Panthers together.
Dating back to the under-16s Harold Matthews competition for Penrith, the pair have won a remarkable 106 of 133 matches they have started together at all levels.
And their potency was evident from the inception of the pairing, after Cleary went from bench hooker to partner Luai in the halves late in the 2013 season.
"Jarome was a St Marys junior and always a halfback," Brett Atkinson, who coached that under-16s team, said.
"In that year with Harold Matts, Jarome was the halfback and organiser.
"But having Nathan come in for the last four or five games, before the end of the season, it just freed both of them up.
"It wasn't solely relying on one particular person."
Back then Luai was going by his grandmother's surname of Broadbridge, and was considered by many to be the generational talent of Penrith's young brigade.
Cleary was a blow in, new to the region after flying in with his father Ivan from Auckland.
"Nathan was always the calm-head organiser, where Jarome could be the off-the-cuff player," Atkinson said.
"They both had a good understanding of the game, and key moments of the game
"That's where they've had great success since, they have been able to complement each other."
Little has changed in the time since, even if Cleary's progression meant he often moved up grades one season ahead of Luai.
NSW have often entrusted the pairing of Luai and Cleary to get the job done. (Darren England/AAP PHOTOS)
After winning four of five matches together in Harold Matthews, Luai and Cleary reunited on-field two years later to take Penrith to the under-18s SG Ball semi-finals.
And while Cleary often moved that little bit faster, the pair remained part of the same weekly training squads through to their NRL debuts.
It's part of the reason why they can create history on Sunday before Luai's exit for Wests Tigers, as the first halves pairing in 63 years to win four straight grand finals together.
"They didn't push against each other, which can happen," Alex Chan, who coached Cleary and Luai in an under-18s squad, said.
"Players get jealous and say he gets all the credit, and they work against each other trying to get the better hand.
"They are so close to each other, they always worked with each other.
"Jarome has always had that little bit of a dig about him, that real cheekiness. He has always been that flair, 'I'm here, give me the ball'.
"Whereas Nathan, he's on."
Melbourne, minor premiers and bookmakers' favourites on Sunday, know there is more to the Penrith threat than just Cleary and Luai.
"They are a well-oiled machine," Munster said.
"I know Nathan Cleary gets a lot of accolades about the way he plays, and rightly so, he is one of the best the game has seen for a while.
"But they have the class of Luai and Dylan Edwards, who just doesn't stop.
"Their team is full of hard-working players with Liam Martin, James Fisher-Harris and Moses Leota, who don't stop either".
Sunday will mark the last ride for several Panthers, with Fisher-Harris and Leota also splitting as front-rower partners.
But for Cleary and Luai, it marks the end of a long road from the training field on Coombes Drive at the back of Penrith, almost 13 years ago.
"It's a long time ago," Luai said.
"I was definitely a lot louder than Nath. But what he has done for me and my development, he set that standard that I have been chasing my whole career.
"It's been a pretty cool ride ... I don't know if I would be here without him."
Australian Associated Press