he mentioned that he has a younger sibling which implies that is jiheon since he knows his mother.. And their face cards.. He probably follows the dad's face whereas Jiheon has his mother's
Jiheon doesn't have a father. His mother was all he had so she most likely had another child and Jiheon never knew about and it's the Professor or maybe he did have a father and that's where Professor gets his looks but yeah I think they are siblings too
yeah ik he doesnt have a father but maybe proff might has his dad look if they both share the same father (split/divorced parents—a guess)
if thats not the case, then your theory might be right—she might have another child with a different man since jiheon's mom basically never rlly was there for him in his life..
as in he doesnt have a present father*
Why is Professor Cha telling the other guy to not mess with Jiheon, are not they love rivals or something?