Joe Penny is quite good at bromance. In Jake and the Fatman, he is younger enough (by thirty-six years) than his co-star (William Conrad) for J.L. McCabe to refer to Jake at one point as a son. However, the show presents them more as friends than a father and son.
In Riptide, Joe Penny and Perry King are peers who served together in the military, then started a detective agency run out of a boat.
In both cases, there is a strong domestic side to the relationship. McCabe drops in on Jake unexpectedly and expects him to make McCabe dinner. Cody and Nick live together on the boat.
In all cases, the young virile detectives pursue girls. But they always cycle back to their home base.
Since Joe Penny is a main character in both, I'll focus on him. And what makes him good at bromance is his unself-consciousness. He is quite tactile, not just with the other main characters but with minor characters, such as his nephew. That is, he isn't afraid to hug and kiss. He is physically at ease. This easiness goes a long way towards selling the bromance relationship.I know that cultural assumptions are...assumptions. However, Penny's mother was Italian. There's a whole science of proximity (proxemics)--how close people are willing to get to each other, what feels natural versus what doesn't--which states that North Americans apparently prefer a distance of about 2-4 feet with strangers. For Italians, the distance is half.
So perhaps, Penny grew up with less wariness about closeness.