Is it ok to charge an additional amount for extra related adults?

[Jason Daubenmire]

Hello...can anyone please share if they know if it is kosher to tell a potential applicant (before they have provided us with the completed application) that our lease will require an additional monthly charge to have an extra related adult (nephew in our case) living in the property with the main family members and their minor children? I have 5 bedroom SFR in Jacksonville, Florida listed for rent and was contacted by a potential applicant that wants to apply to move 9 people into the place. 4 adults (Husband, wife, mother of wife, and nephew) and 5 children. I have the property listed for rent at $1225/month. Would I be in any violation for requiring an additional monthly charge for the adult that is not immediate family (the nephew) and require larger deposit (refundable of course) than originally advertised on Craigslist due to the large number of people that would be living there? Gracias!