Different occupancy limits for children vs adults?

[Megan Fitzgerald]

I'm renting out a fully furnished renovated 3BR 1.5 bath townhouse in Philly, advertising on AirBNB and Furnished Finder. 

My first renter is a family with 4 kids. I'd stated the occupancy limit on the property is 4 adults and was a bit unprepared when he filled out the application with 6 total people (himself, wife, and 4 kids). But the laws seem OK with 6 as an upper limit for 3BRs so I went ahead with the rental. 

I'm OK with having a family with a few kids (6 people is pushing the limit, but a number of families on our block have 3 kids in the same size home and it's fine).  But I truly can't have 5-6 adults in the space-- it's only about 1100 sq ft. Adult roommates cohabitating on my block tend to live 2 per building and keep the third bedroom, which is small, as an office or guest room. 

I'm wondering how to advertise the space going forward. The space is most appropriate for a couple with 1-3 children, 3 single adults, or even a couple with a grandparent or nanny and a kid or 2.

From what I'm reading, the law protects families with kids from discrimination, but can I get in trouble for doing the reverse and allowing (and potentially advertising) a higher occupancy rate if people have babies and children than if all occupants are adults? 

[Russell Brazil]

General HUD guidelines are for 2 people per bedroom plus 1. So a 3 bedroom apartment 7 people can live there if they are related.

Unrelated people generally will need to adhere to local regulations on unrelated people. In Philadelphia I believe that's capped at 3 unrelated people.