Legal Question in Real Estate Law in California

First, as to the joint tenancy. Assuming your brother is still living at the time your mother passes away, he will become the sole owner of the property. This will be true as a result of the way joint tenancies work, and whatever your mother has written into her will won't change it. You and she should consider whether severing the joint tenancy and converting it to a tenancy in common might better reflect her desires as to who gets the house when she passes away. The process of converting a joint tenancy into a tenancy in common is very simple--it involves her writing up and recording a brief declaration of intent to sever the joint tenancy as provided in Civil Code section 683.2. You and she may need a real estate lawyer to assist in determining whether this is something you want to do, then to prepare and record the declaration.

Next, the notices she has received regarding property taxes sound like the usual and customary notices the county tax collector sends to anyone who is behind on tax payments. You need to sit down with your mom and go over her records (checkbook, etc.) to see whether she has paid the property taxes in recent years. Probably not. Then, find the most recent bill or notice, and pay the amount due. Perhaps a personal visit to the office of the county tax collector to pay in person would be advisable, to verify that the amount is correct and to obtain a receipt. Failure to bring the property taxes current will result in a sale of the property for unpaid taxes and your mother's eviction.

Nothing to become the sole owner of if the taxes don't get paid. It sounds like the property taxes are in default, which can cause the property to be sold at a tax foreclosure sale if they are not paid.

Rather than seek speculation and worry about this, contact the taxing authority to determine what the bill is for, and resolve it. If this is about real property tax that is unpaid, it will have to be paid to avoid foreclosure at some point. If it is for some other reason, and correct, then work out payment on it.

As to the joint tenancy, she'll have to get his signature on a grant deed or quit claim deed returning his share to her, or other form for title transfer, if that is her desire. Otherwise, he is an owner that will get title to the property upon her death. She must make sure she does not create a taxable event.

She needs the help of experienced local counsel to make sure these things get done correctly.