i think it was really hard for ace to see why would have sabo wanted to be his friend. i mean i imagine he was asking questions about roger before sabo and deep inside hating himself for the blood of his. and when he met sabo he didn't want to do anything with him. but he was anywhere he went. and he didn't like it and wanted to scare him away. but sabo was stubborn ofc so he followed him anywhere and then something happened where sabo helped (?) ace or something and ace started to trust him.
yeah!  along with the problem of his blood, i feel like the people in the gray terminal kept pretty close to themselves and their own families, so they probably wouldn’t want anything to do with him, and dadan and the bandits didn’t really want to at the time either…it’d be hard as a kid (or…as a person in general) to not feel on edge and resentful about being that isolated.  i imagine he had to be really independent since a very young age.
i don’t think sabo would be quite as pushy as luffy when it came to befriending ace- but sabo also seems like a good judge of people, so he could probably sense (like luffy!) “hey this guy is someone i wanna know, esp since there’s really no one else” and be pretty resilient about getting closer to him.
i can def picture a situation where ace got himself in a bind with something/one that was more than he could chew, and sabo helped him. Â
AND i just thought of this- we gotta remember that sabs is just coming out of living in a comfortable town in a comfortable home, i doubt he really knew how to fight at all, so that might have been a barrier between them at first, like ace was like “this loser’s so weak, i’m not hanging out with him” but then sabo did something to prove him strength, whether physical or mental, that at least -started- to catch ace’s interest….
….ooh…OH THE FIC IDEAS ARE STARTING TO ARRIVE….I CAN FEEL A STIRRING WITHIN ME….