Upon death, the dead person's interest automatically passes to the survivor. There is nothing for the son to inherit, here.
And if the loan is in just the decedent's name, it is a claim against the estate. But if the survivor also signed the mortgage lien instrument, the property is pledged as security and can be foreclosed.
You do need a lawyer to review your documents and walk you through this.
Yes, you should have legal help. Even one little detail could alter who gets what. Best to know the score so that even if you get nothing, you do not wrongly resent someone in the family.
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