Hello,
Since this is her home you can not evict him regardless of who pays the bills. He is permitted to live there by the owners permission. If you do not want him there your right is to leave the property. Since you do not own the property and he has permission to be there eviction would not be permitted.
If he is causing harm you could in essence call the police and ask that he be removed for his behavior. Though once things cool down he would be permitted by law to return. But keep in mind if grandma really wants him there she could evict you and your wife and then allow him to return to the property.
I wish you the best,
Walter
Legal C&onsultant
Specializing in all aspects of law including Family, Real Estate, Employment and Consumer Protection