Legal Question in Real Estate Law in California

There isn't enough information provided to give you a full and dependable answer. Among other things, the answer depends upon whether your father had a will or trust, and what it said.

The greater probability is that you and your three siblings are equal co-owners. This would be the result under many wills and, in most cases, when the parent is single and dies intestate (without a will or trust).

Co-owners (equal or even unequal) have a shared legal right to possess and occupy 100% of the co-owned real estate. In effect, they are roommates under the law.

However, this doesn't mean your sibling has the right to show up and move in. His or her right to co-possession must be exercised in a way that minimizes the likelihood of a breach of the peace. Indeed, there is a legal procedure for a co-owner who is out of possession to assert their right to enter and occupy the property. It's set forth in the Civil Code at section 843, and you can look it up on line.

So, your problem basically has two parts: what can you do in the short run, and what is likely to happen in the longer run. And, the basic answers are that in the short run you can probably get away with telling the co-owner "no" to moving in, and the sheriff won't help him or her........but sooner or later, the co-owner may get a lawyer and follow CC 843 procedures.

Ultimately, someone among the four co-owners will probably sue for partition, under Code of Civil Procedure sections 872.010 et seq. This is the law that allows a dissatisfied co-owner to demand that the property be sold and the net proceeds (after paying off loans and costs of suit and sale) equitably divided among the former co-owners. Partition is a near-absolute right of co-owners.

Finally, the rights of co-owners can be adjusted by contract. For example, the owners may contract with each other to allow one of the owners to have an indisputable right to sole possession, usually for rent or some other consideration. Also, co-owners can waive their right to partition. However, none of this is likely a factor in your situation.