How to evict a co-owner of a house?

All legal owners of of real estate have rights to it. In the case of a residential dwelling, that means that all parties holding title have the right to reside in it. However, you still have legal recourse in such a situation.

When co-owners of property cannot agree as to ownership matters, there is a judicial remedy called "partition" which can be enlisted. In a partition action, a suit is filed to determine all of the owners' rights/responsibilities. The court can order that the property be equally divided, to the extent practical. However, in the case of a  single family house, the court can order something called a "sale in lieu of partition". Pursuant to this, the property is put up for sale and at such time as it sold, the proceeds are distributed equitably among the parties.

Note: Prior to a sale, the court will first give the owner who wants to keep the property the right to buy out the other owner(s) for fair market value. 

Unfortunately, under the laws of all state sin this country, unless there is a written contract to the contrary, all owners of real property have the right to reside within it. The problem that you have is a buyout or partition situation with respect to the one sibling that moved into the family home. You cannot legally evict him or her from it due to the joint ownerhip issues.

I recommend that you consult further with a real estate attorney as to how to possibly have a buy out of the assorted family interests in this family home.

To sell the home if not all owners agree would require the filing of a partition action in state court and an order from the court that the home needs to be sold.