I'm a co-owner of property and my brother had renter unknown to me? How do I evict this person (s)?

Assuming that you and your brother own the property as co-tenants, each of you has a right to use the whole of the property so long as your use does not interfere with the right of the other co-tenant to do the same. This concept can create lots of problems where the co-owners are not cohabiting or have not arrived at an agreement as to the usage. Your situation, which is not uncommon, is a good example. I disagree with the advise that you should commence eviction proceedings as you may discover that your brother entered into a lease agreement with the tenant as he has a right to do. Also, where have you been for the last six years? The court might determine that you have been sitting on your rights and that you have acquiesced into the arrangement. You have a two pronged remedy. You can sue your brother for an accounting for the rents he has received. You don't say anything about how the taxes, insurance and maintenance (and mortgage if any) are being paid for. If your brother is doing that, he would be entitled to an offset against the rent. This kind of suit tends to degenerate into an accounting mess and doesn't end the problem.

The second remedy is a suit for partition. In California, a partition action generally results in a sale of the property either at public auction or through private sale. Partition actions can be costly, but they are common between family members that have inherited properties as this seems to be. You can read about partition actions at www.partitionlaw.com. I do not handle them but serve as the referee, which is a court appointed position with responsibility for managing the sale of the property.

You would have the right to bid in the sale auction and would be entitled to a credit bid for your half of the property. Partition actions often result in settlement and this might be the best way to get your brother's attention. You would also be entitled to the same accounting mentioned above in the context of a partition suit.