What happens if A borrower dies after loan assumption in Tx?

[Eboney Jones]

Got an odd situation. Working with a lady in Fort Worth, Tx who took over payments on a home back in 09. She signed a warranty deed for it and was making regular mortgage payments until the borrower died in 2015. She tried to refinance with the lender but was told she had no interest in the home and that it needed to go to next of kin. She still lives there but hasn’t made payments in almost 5 years. She has a warranty deed that was signed by the previous owner and everything. She wants to sell but I am unsure if I need to track down the deceased owner’s son to do some sort of affidavit saying that he relinquishes his interest in the property or if the warranty deed would take care of that. Any advice? TIA