Security deposit from multiple tenant

[Tom R.]

My tenant has asked for a roommate. The tenant has already paid a security deposit and a pet deposit. If I charge a security deposit of 1 months rent to the new tenant the total security deposit charged to both tenants would be more than 2 months the total rent paid by both tenants. I'm pretty sure the answer is no but can I do this or do I have to keep it at a maximum of 2 months?