Legal Question in Real Estate Law in California

Your question isn't entirely clear because you say, first, that the property is held by two married couples, then you go on to say that one couple was bought out by the other. My first impression is that the entire situation should be reviewed, in person, by an attorney with real-estate transaction experience -- that shouldn't be too expensive because it doesn't seem likely that any litigation is in prospect; it's mainly explanation and maybe some document-preparation and filing. Possibly a title and escrow company could provide the necessary review and explanations, particularly if one has previously been insuring title. In any case, whether there has been a change in borrowers or also a change in ownership, it is very important to have documentation, recorded when permissible, accurately reflecting the current status of both ownership and borrowings affecting the property.

Deeds of trust transfer automatically when the promissory note is transferred to a new party. That's because a deed of trust is simply security for an underlying obligation.

I agree with Mr. Whipple that it seems your terms may be confused, as it would appear that you are referring to ownership of property evidence by a deed.