Unapproved tenant in property

[Daniel Walton]

So with a recent tenant moving out I’ve since discovered that she had a boyfriend staying with her in my property. He was not listed on the lease but upon them searching for another apartment he listed me as his current landlord...even though I never met him. Since I’ve been at the property doing some painting he has had a TON of mail coming in, confirming this suspicion. The tenant left the apartment in good shape but has broken the lease by not having him listed as an occupant while he obviously was. Am I in the right to keep the deposit since the lease was broken or am I nitpicking?