If he’s married and the condo is in his name, depending on state laws, how long they were married for, what the expenses between them were - the likelihood is the equity in the condo will be split between son and ex wife
Unless there was a contract prior that the wife also signed honoring the mother’s contribution and stake, the son would have responsibility paying the mother but I don’t see how the ex wife would be involved
Assuming ofc that $ went from mothers account to sons, and not directly to the condo loan. Also assuming the son didn’t claim the $ as a gift and paid taxes on it, and instead paid no taxes on the $ hence treating it as a loan
Not a lawyer ofc , let us know what happens I’m curious