To be fair, they are not his family. Just some stranger he found out are supposed to be his family. And unlike them, Mc has already spend so much time with the other characters n created a bond with them.
Also, this isn't really the end, the manwha just got canceled, I recommend reading the novel, way better.
I mean his real familyyyyyy in irll
Nooooooo...!!! What makes you think that??? He didn't choose them over his IRL family, he just doesn't know how to get back to them! Like he tried once, the ml yanked him back (in the novel) the ml was so scared Mc was gonna leave him....ain't that obsession? He was all like, u were gonna break ur promise? U were gonna leave me....!
such an ugly ending wdym u chose them over ur family that fast???