There's a good chance that the deed to the trust severed the joint tenancy and put your parents' interest into their living trust, but you should have an attorney review the trust and the deeds to give you a definite answer. The law dealing with severance of joint tenancies is at California Civil Code section 683.2.

As Chris says, it is possible that the deed to the trust severed the joint tenancy, putting your parents share into their trust and leaving you with your one third share. Depending on what the documents say, it may well have ended your right of survivorship. There are a number of other arguments your brother could make as to why you should not, in effect, get two thirds of the property (your one third and half of the other two thirds). All of these depend on the specific facts of your situation and what the documents actually say.

IMPORTANT NOTICE: The above response is not intended to, and does not, create an attorney-client, fiduciary or other confidential relationship with the responder. Neither does it constitute the providing of legal advice or services or the giving of a legal opinion by the responder. Such a relationship can only be created, and legal advice and/or legal services provided, pursuant to a written agreement with the responder. Accordingly, no obligations of any kind are assumed with respect to any matter or question presented. It should also be noted that legal issues are often time sensitive and legal rights may be lost or compromised if you do not act in a timely fashion.

The conveyance by one or several of the joint tenants into trust severs the joint tenancy. You now have a tenancy in common.