Thank you for your reply. We are in the process of finding a lawyer. Since we are not along the coast, it’s difficult to find a lawyer who is able to help us in English. We both speak very good Spanish but not enough to read legal jargon and understand its implications. It also seems to be difficult to find a REPUTABLE English-speaking lawyer along the coast!
At present, we have been advised that the long lost brother IS still alive and MAY have signed some kind of ratification document after the house was purchased. The vendor and her lawyer are currently trying to track him down.
Thanks again for your advice.