Legal Question in Real Estate Law in California

Yes, someone who paid part of the down payment for real estate is often entitled to part ownership under a principle called “purchase money resulting trust”. There is a somewhat involved formula in the law for calculating such a part interest, and her brother’s share is likely to be rather small, but nevertheless needs to be determined and respected. I suggest finding a lawyer who is familiar with resulting trusts, which may not be that easy as the concept is rather obscure.