Who did you rent to? Were you aware that these two would be living with the SIL? Who is paying for the food they are eating? Were there any discussions about cleaning up after themselves?

Is there a written lease? Is the lease for a term, like six months, or a month to month lease? If it is a month to month lease, give them written notice that you are terminating the lease at the end of the month. The notice has to be to the leaseholder. Since your SIL is paying the rent, I assume the lease is with her.

See here: http://www.formsguru.com/forms/legal.../notdelpo.html

Send the notice by certified male return receipt requested. Send the notice to the two in the house also. Get the notices out so the people have to be out by the end of April.