it has been revealed that Haejun stopped believing in middle school - about the promised return of his mom.
Although one can still hope continually but long goneis the desperation as if your life depends on it. He may sometimes get jealous and get emotional but he knows he can continue life even without his mom.
Sanha on the other hand, he described the relationship as toxic. It made him hate himself, to salvage the affection left he has for his mother and dead sister. He needed a lifeline to literally live life and be allowed to enjoy it. He found this with Juwon.
I think we must also consider their personalities. Haejun does not have any parents, but I still feel for Sanha because I have a closer personality with him. I am reseved who thinks and feels a lot of my surroundings.
Lastly, the tie breaker there was grief of losing someone to death. This weighs more for me.