My parents are going through a lot with my brother at the moment. He constantly steals, destroys their home, expects everyone to clean up after him, threatens to burn their home down, etc. They were told by a sheriff, who they called when he was threatening to burn down the house, that they cannot remove him from the home if he has nowhere to go.
He is 18, which is the legal age of an adult in Ohio, does this mean they have every right to remove him from their home?

Evicting a resident of your home is the same whether they are a relative or not. You have to give him 30 days notice to vacate. If he has not left by the deadline, then you go to court for an eviction order.

However, there may be a shortcut. If he is making threats, you can try for a restraining order to keep him away.

Hope this helps your parent and you How to Evict an Adult Child | eHow.com