How to get the ex-boyfriend to move out!?!?!

[Phil Goodwin]

A family member lives in Florida and rents a home.  Lease is month to month.  The ex-boyfriend (and his 3 kids) moved in this year in the hopes of making amends.  Unfortunately, it did not work out and he is verbally abusive.  He is not on the lease.  The landlord provided a verbal approval for him to move in.  Nothing is in writing.  She is so stressed out with the situation that she decided to stay with a friend temporarily (starting last week), she plans to continue to pay the rent so that her credit does not get damaged.  He is not contributing toward the rent, upkeep of the house, utilities, etc.  He keeps saying that he will move out but he is not even looking for an apartment, he is just milking it.

How does a lessee get a non-lessee (and his kids) to move out of her rented house?