Legal Question in Real Estate Law in California

It may depend upon the language of the specific trust deed. In some forms of trust deeds, where there is more than one beneficiary, any of the beneficiaries can substitute the trustee, and the substitution is effective

The more general statutory rule on this is set forth in Civil Code section 2934a, and is a little complex, but a majority of the beneficial interest seems to be able to cram down a substitution against a minority if there has been a default. If no default, it appears the beneficiaries must act unanimously unless the trust deed provides otherwise.