okay so, i have this long standing headcanon that buck and tk have stayed in contact this whole time. they're eachother's online besties, not that they would use that word (rival? frenemy? block bait?), it's a lot of trying to one up eachother about calls they went on and other aspects of their lives, the occasional disscusion about new nature docs book club style, but mostly it's just memes and shitposts.
once tk retires to stay at home dad jonah the one upping becomes a lot about how they're doing in that aspect of their lives instead. tk is bragging about jonah, buck is bragging about chris, buck is hearing all about cool things carlos has been up to, tk is suffering through an oblivious bisexual man whose favourite word is eddie.
they end up pushing each other to be better boyfriends/husbands/parents with their weird little dynamic, it's very 2 competitive people with some kind of neurodiversity going on just enjoying having an outlet for that energy where it's welcomed and won't be taken in the wrong way.
buck probably comes out to tk all serious and tk, who assumed he was aware and has been talking to him like he knew this whole time (we're talking sending him bi specific memes nancy sent him), is so confused. tk's response is quite literally a single question mark and that's when buck finally remembers the 'i already have a boyfriend' comment. tk probably apologises saying he genuinley thought buck already knew, buck doesn't really mind because this is all quite funny in retrospect. tk is however shocked that not only did buck have this revelation, but eddie wasn't the cause of it based on all the complaining buck was doing that eddie's attention was elsewhere. tk would probably have to hand his phone over to his husband so he doesn't tell this man that maybe, just maybe, it was eddie he was after all along.
i think in a universe where they do stay in contact i can kind of see tk playing a small part in buck's opiate recovery too, probably not something he finds out about until post detox with a message that's just "sorry i haven't said anything in a couple days, my family took my phone while i was in withdrawls" and tk's response is "yeah been there bro, it's all good" and they just bring it up again occasionally from there, offering mutual support when the other needs it. the tone shifts in their conversations can be a little jarring to the average person.
for as often as they talk and consider each other a friend in some way, buck is so thankful austin is 8 hours in the wrong direction from el paso, because if they ever met up in person he's pretty sure it would be a disaster, they work best as instagram pen pals. buck is not aware that tk has family in santa monica, a 30 minute drive from la.
if they do ever meet i can imagine it being at the zoo, theo befriending jonah in the play area because he was talking about the firefam and jonah wanted to join in because his papabro used to be a paramedic. when buck and tk finally see each other, it's just them glaring at each other and only dropping it when the kids start picking up on the tension, doing a full 180 into a hug like they're old friends from college.
very important that eddie doesn't recognise tk so he and carlos can have an awkward conversation in spanish off to the side about sports the other doesn't like before figuring out how their husbands know each other. carlos would be thoroughly amused and confused by the buddie timeline, he'd also make a comment about how both eddie's kids look like buck and eddie having to admit out loud that he has a type and chris looks just like shannon before getting into the theo backstory.
