weird

i would like to get some opinions. My fiance has what I consider a weird relationship with his sister. She is currently living in our home and she goes every where with him. He is an independent contractor and she goes to work with him and spend all day with him. we do not spend any time together as I am at work and when he comes home he sits in the garage watching tv with her. When I tell him that I want to spend time with him he comes to the room and go to sleep we don't even talk anymore. we last had sex a month ago and before that we have not had sex in two months. How should I handle this?