Do guys befriend guys who are interested in their gf? Is this a thing?

Hear me out, there’s this guy that I know from when I was younger back at home in my country we never hanged out properly or anything and we talked on Instagram rarely, and when me and my bf got together and I posted pictures on Instagram he’d leave a positive comment of ‘well done bro’ or ‘good for you guys’ sort of things and I think he followed my bf on Instagram, now I find it soooooo strange my bf was so keen to befriend him, I later realized that years before I got with my bf I left comments on the guys page with like ‘🤤🤤’ and my bf must’ve seen them, so why tf would you want to be friends with that guy? I wouldn’t lol if it was happening vice versa, ANYWAY yesterday the guy sent a happy birthday to him and they were talking and my boyfriend asked does your brother know him and I was like yeah I think so and then he said ‘does he like him?’ but he seemed so idk weird when he asked that, as if he was scared my brother likes that guy more than him. Maybe I’m overthinking it, but I don’t understand why he’s want to befriend him so bad, I don’t even talk to that guy

And also in the title I said guy who is interested in gf because back before I got with my bf he used to text me, sort of flirtatious, but it didn’t last and I assume my boyfriend thought we had a thing bc I left emojis on his post back then😭 which meant absolutely nothing