Legal Question in Real Estate Law in California

By a quiet title action against the heirs of that lender. If any exist, you will likely end up paying off the note and interest to get clear title, or at least negotiating a settlement with them. Consult with local RE counsel for help. .

Also note Civil Code sections 882.020 et seq. applying to "ancient" deeds of trust and mortgages. It could be that the 2nd mortgage here will before long become unenforceable due to the passage of time. Since the holder can revive the obligation if they become aware of it, maybe lying low for a while might be a better strategy that attacking with a quiet title suit.

You can't quiet title to an ancient "mortgage" without paying off the debt. That's the origin of the "tender" rule, and that is the original application of the tender rule.