Okay JoR relationships one by one for funsies
Ronan & Finn
These two are the first two in the team, and the ones who pretty much know each other best. They've both rescued the other, and they have a unique sort of brothers-in-arms relationship where they appreciate the other and the other's combination of abilities, specialties, and even unique flaws.
They're the perfect complementary pair: A young angry long-range fighter who's always ready to fight & An older/wiser Peaceful Melee fighter who's ready to negotiate and talk things out
Their ranges of Cool vs Hot-headed cover a wide spectrum, and allow them to get a variety of things done that they couldn't do alone
Ronan:
Ronan is rescued by Finn when they meet, and he's intensely distrusting at first, though he eventually warms up and asks Finn for his help because he knows that if he gets into a particularly bad fight, he's going to need a retreat strategy, and this kindhearted man who offered to help him is likely his best bet.
Ronan admired Finn's patience & Ability to make intelligent and careful decisions that allow both of them to use their abilities to the fullest extent, and he especially admires Finn's kindness and determination to fight for the good of others. On top of all these things, Ronan was first drawn to Finn when he noticed the man's talent with combat, and he's absolutely obsessed with having Finn teach him better policies for Melee combat.
However, Ronan dislikes the fact that Finn is a bit of a stickler for the rules, and judges his violent habits due to his own goals and priorities when it comes to teamwork and lifelong aspirations. He's also often dissatisfied with how Finn prioritizes keeping him safe over the overall effectiveness of the mission because he doesn't want to be treated like a child, and he just wants to fight.
Finn:
Finn first finds Ronan fighting for his life with a pair of brass knuckles against an ambush by a group of thieves, and he's intensely impressed by the fortitude of this weird kid. He wants to help him instantly, but he never expected this weird 17-yr-old to have one of the most bizarre stories he's ever heard, and he instantly decides that he has nothing better to do, so why not escort this guy around and help him out. It's the least he can do.
Finn admired Ronan's resiliance and competance with his resources, as well as the fact that Ronan is obsessed with properly rationing and preserving resources, namely food and money. It concerns him slightly how resourceful and adept this kid is at using literally anything at his disposal to create tools for survival, but he does admire the determination and sheer energy to fight and consistency to stand with honor, even if he is a little violent for Finn's tastes. Finn was also impressed by the humility Ronan showed when asking him to join him and how instantly he shifted Finn into a higher leader position and was ready to do whatever he asked, though not without sharing his own opinion.
Of course, though, every partnership comes with flaws, and Finn is extremely not a fan of how reckless and violent Ronan is. Every day with him, Finn has to remind him not to act impulsively, and if he wants to negotiate instead of fight, Ronan is more of a hindrance than a productive ally because he's always right behind Finn glaring at the enemy with his hand on his weapon. Ronan's sheer determination is good, but he's sometimes a little too persistent, forcing Finn to grab him by the collar so he doesn't hurt himself. Ronan also isn't the smartest, socially, street-wise, and especially not book-wise, and Finn has to reason with him constantly because once Ronan is on board with a plan, he sticks to the plan.
Overall, these two like one another a lot, Finn & Ronan see each other as a surrogate Father/son but also a reliable combat partner whose opinions and skills they value even if their priorities are very different, instantly bonded by trust and the need for someone to watch their back in combat