Legal Question in Wills and Trusts in California

The decision as to who is trustee belongs exclusively to your parents. Legally, you have no say in the matter.

The choice of successor trustees has no impact on your share of the trust. You would be entitled to receive fifty percent regardless of who was the successor trustee.

It is impossible to evalue the chances of your sister bringing suit without knowing a lot of details about your family and the trust.

I agree with Mr. Perry and write to answer the part of your question about control. You are partially correct about having no say. You would have no say in the basic administration of the trust. The trustee, however, would be under a binding legal obligation to manage the trust property in a way that is the most beneficial to you. That is called a "fiduciary duty." It means that the person with the fiduciary duty must exercise as much or more care in the handling of the trust as they would their own financial affairs AND what they do must be objectively reasonable (meaning not just they think it reasonable but that a normal rational person would agree it was reasonable). It also means that they must put benefit to you on the same level of priority as their own interests, or higher. If they fail to fulfill their fiduciary duty properly, they can be removed as trustee and forced to pay for any losses to the beneficiary their failure may have caused. So while you lose direct control, you gain substantial protections under the law by being a beneficiary without being a trustee.