Maybe, maybe not, if it's based on occupancy. The baby means the population doubled, with Dad coming 'home', tripled. An awful lot depends on the terms of the lease.
No, I'm not arguing in favor of the landlord, either.
I'm just saying that it doesn't seem as if we have the whole story.
They in turn (as per their lease) sent him a response indicating the circumstances. 7 days is an arbitrary number. It will not hold up in court.....the question being...is he a visitor or a resident.