Is sitting far away from one's father and siblings—who watch TV a lot and sometimes pray at home (late)—considered an act of disobedience to parents (ʿuqūq), and is it better to continue in this state or to sit with them despite the presence of a reprehensible act, while disapproving of it in one's heart?

You should advise your parents and siblings to stop delaying prayers and watching forbidden TV series and movies, explaining the religious ruling to them gently and politely, without violence or abuse. If they do not respond, do not sit with them when they are watching forbidden things, but there is no harm in sitting with them at other times and treating them kindly so that they may accept your advice.