Legal Question in Real Estate Law in California

You need to revise your question. It makes no sense as asked. You mention a deed of trust, but you never identify who the deed of trust holder is and then it disappears out of your question. it appears to say A&B are the lenders under the deed of trust under a joint tenancy agreement in the security(?) (I THINK that is possible, but I'm not SURE you even CAN be the beneficiary of a deed of trust as Joint Tenants). Is that what you really mean? You also totally leave out the terms of any agreement or other grounds for "reliance" upon which C gave a quitclaim deed, and why C would have any interest in whether A and B are JT's or TIC's, especially after C has abandoned all interest in the property (it seems).

We title lawyers are linear thinkers - mostly because the law of title is totally linear. So you are going to have to outline what you are asking about, step by step, transaction by transaction, in chronological order, to get a question we can answer.

With all that said, however, I CAN tell you that if B violated any agreement with C regarding the making of deeds, holding of title, etc., it would NOT EVER void the quitclaim. Very few things completely void a deed. If there was fraud in the inducement to give the quitclaim, it might be voidABLE, which is similar but not the same in many ways. A mere subsequent breach of contract, however, would not have ANY effect on the validity of the quitclaim. It still might, however, give rise to a cause of action for rescission, but that is also somewhat similar but very different from void or voidable.