Lost lease, tenant issue

[Matthew Steele]

Hi first post here just looking for advice, I rent a multi family home 2 unit for about 15 years have been lucky to have both units rented for 10 years no issues, well until now. The tenants in back apartment were married, was informed by the female that they were getting a divorce but she would be fine paying rent alone. OK. A week ago I received a shelter verification form from DSS for a male individual who I don't know at my apartment. I contacted the female renter and asked what was going on and she said he was living there, my lease like most leases states tenant must inform me if someone else wants to move in and cannot sublet, I always keep all my rental agreements in one spot and I don't have hers so now what do I do? I'm sensing this new guy will be trouble, should I allow him to go on new lease or evict both, I'm so mad I can't find our agreement anywhere, let me know, thank you for your time