Renter's boyfriend has moved in.

I rent my lower level of home. The first person to rent from me was a young guy. He talked me into a 5 vs. 6 month lease. After 4 months his ex girlfriend moved in and he moved out. Now they are back together. They have a 1 year old. He is now always in my lower level if not at work. I pay all utilities and they have gone way up. He showers, does his laundry etc. WE share laundry and my kitchen. He never comes to kitchen area but is constantly here. What should I do? I dont even like him very much. She is very nice. The rent is super cheap and utilities are included. No lease for her yet.