Have you aksed for him to leave as he was not part of your rental agreement? Regardless since this is a month to month tenant you can give tenant and Bf a 30 day notice to vacate. If they refuse then you can begin eviction process. Refer to site below to be sure you do everything legally
Do I need to give both tenant and BF separate notices or can I give just the roommate the notice?
The form I was going to use starts:
"TO_____________________________________________________________
and all other tenants in possession of the premises described as:"
Can I assume that the BF is included in the "all other tenants in possession of the premises" portion?
I'm not sure if this is relevant, but for some reason I'm concerned that handing the BF a 30 day notice to quit would some how enable him to full tenant rights or is he considered to have them already?