unauthorized occupants, can I raise rent? prop mgr says no. NC

[Wendy M.]

Single mother and her 2 teens are on lease (March 2020) but she really moved in with her 27 yr old daughter plus her 4 kids, as well. Neighbor let me know as he had a friendly chat with them when they moved in. I told property manager at that time but they said nobody else lived there but people were helping them move in. Turns out neighbor was right and they lied back then because on a recent visit where I had to fix a problem the adult daughter verified that she was living there from the start. Told me she was not on lease but pays rent to her mother.

I went to property manager with this info and was told they can't do anything since they're family other than give them the opportunity to have her fill out application and be vetted and if she is approved by them then she can stay. I asked them to raise the rent for the remainder of lease as the terms (how many people were living there) had changed. There are 7 permanent and 2 part time residents now (the mother's college age kids who are home "due to covid" and schools being out.)

Is it not possible to raise the rent due to so many previously unauthorized tenants?  I am in NC.