Legal Question in Wills and Trusts in California

You have a complicated situation - it appears that your father held everything jointly with his wife, or that he didn't have any separate property. The reason I say this is that your father's children would have inherited two-thirds of any separate property subject to probate.

You haven't given us enough information to really answer your question because we do not know how your uncle got your stepmother to provide you with anything - was there a lawsuit, or did he just persuade her into making a provision for you and your siblings? If there's a trust, then we need to know the terms of the trust, because that will control what your uncle may or may not do with whatever was left to you (or given to you) by your stepmother. You should review this trust document with an attorney.