Agreed to help father in law get back on his feet let him move his rv on my property have asked him to leave more than once he refuses have plenty of reason why he needs to go help?

Verbally telling him he never has to leave. You need to give him a letter stating he has xx amount of days (depends what state you live in) to leave the premises. Then if he still hasn't left you need to go to the district court/magistrate and file formally for an eviction. When the time is up and he is still there the magistrate should send the constables (who whoever your state uses) to remove him.