Knowing is different from understanding.
Both Dojin and Byul grew up only knowing families who love & care for them. They don't know what it's like to be abused and abandoned by your supposed caretakers. So even though they're consciously aware of the fact that Hyesung went through all those and feel bad for him, they can't relate to his trauma. They probably just naively think connecting with family is good, because they subconscious equates such connections to receiving more love.
I could see where they're coming from & that they're not ill-intentioned, but I agree they're really not approaching it right. Sincerely hope Hyesung could get resolution and closure after this.
i think the best ending for hyesung is here to just fully cut off his mom. maybe in his standpoint, he can understand why his mom abandoned him, but he can still never forgive her. i think that's the most ideal situation for all tbh.
but atp, idk why dojin is still pushing for a connection with hye and his mom when he knows what he has been thru. like my boi, use your head for once guhdamn.