Yes. The parents are either dead (and nobody there knows because everything's cut off), or they can't get through to anybody to check on said kids. Or they're busy dealing with the revelations and trust Takatora to take care of Micchy.

(Takatora taking his sister to the doctor might be a bit scary, given that he's concerned but kind of crap at showing it, and Michi's busy trying to appear vaguely sick so that her brother doesn't suspect she's doing this to get birth control when she shouldn't be active. Thankfully for her, she does not get bad cramps.)