Cole (oc belongs to Hinokit) doesnt have the loving brotherly relationship with Jasper, since they were kids they had a wall between them. Jasper doesn't confined in him for anything especially his love life.
In the Fall arc Jasper visits Cole university for a college tour. Jasper has been stalling to go to college for a couple years because nothing interests him. After the summer arc Leon gave Jasper back the ring essentially breaking up with him. Jasper felt crushed and very angry so he decided to go on the college tour to get his mind away from everything, he felt if Leon can move on so can he.
During the visit Jasper meets Cole roommate Sergio (Hinokit OC) Jasper finds him to be a creep with the way he speaks about women and just an overall pompous attitude. Cole wasnt happy to play babysitter and ditched Jasper to go to a party leaving him alone with Sergio. Jasper was very upset, sure he didn't want to spend his entire time with Cole but he wanted to be the first one to ditch.
Overall, Sergio and Jasper began to drink and talk, Jasper began to notice that Sergio was flirting with him. Sergio complimented Jasper on his looks telling him how beautiful he was and comparing him to a woman. Jasper was obviously annoyed yet it has been a long time since he slept with anyone or even fooled around. Jasper decided to take the lead and they slept together. after all, the reason Leon and Jasper broke up was because Leon told Jasper he was inexperienced and he wanted him to explore his sexuality, so the hell with it.
overall, the next day the brothers headed home and stopped at a diner, Cole felt something was off with Jasper and he felt maybe he can ask what was wrong. Jasper refused to tell him. Cole asked him if it was something Sergio had said since he knows Sergio can be an asshole. Jasper told him no.
This isn't the last time we see Sergio, Sergio gave his number to Jasper and told him if he ever needed a friend he be happy to talk. god there so much to talk about Sergio actually but we can leave that for next month