These are my opinions:
Also spoilers
Gyeonwoo was essentially forced into a poly situationship. With him being taken advantage of while drunk. Ido’s commitment issues are caused by his unhealthy attachment to his “friend” (and I use this term super lightly) that he constantly bullies to basically test how far he can push him until “he eventually can’t take anymore and leaves” (LIKE A GODDAMN FRIENDSHIP TEST) he is deeply in love with Gyeonwoo but thinks he stays out of pity for him (ido). Ido won’t commit to any relationship emotionally because of his emotional ties to Gyeonwoo. So I believe it when Jin said that it hurts him when he gets dumped for not being all in on a relationship. It must really reinforce his fears and belief that everyone will leave him in the end. He only accepted being in a relationship with Gyeonwoo because of Jin’s interference (aka stalking and breaking and entering) despite his fears. But, honestly Jin has become another obstacle in ido’s mind. He is trying to force this unhealthy relationship to continue as a mediator for his own satisfaction (is what it feels like). Gyeonwoo and Ido suck at communicating. Gyeonwoo escapes his issues inward (shutting down) while Ido, escapes outward (relationships). So in a way they “need” Jin. But, honestly I hope to see Jin showing genuine love and respect for not only his relationship with them separately but, also their relationship together.
The Shape Of Us