<human>: (This is currently taking place in the state of Texas)

My father passed away about a year ago, and my mom can no longer afford the mortgage for the house that they bought together. Someone wants to buy the house, but she is having trouble selling it because my dad never wrote a will, and to top it off, he had a son from a previous marriage. From what my mother and I understand, him and his other son never contacted each other (at least since I was born 22 years ago). My father never talked about him and his whereabouts are unknown. We only know his first and last name and his mother's first and last name, but no conclusive results have come up from my basic internet research. His and his mother's last names could have changed as well... but the point is, the title to the house can't be released without the consent of the son from his previous marriage, due to some law in Texas. My mom really can't afford a lawyer or anything so any legal or financial advice would be greatly appreciated!  
  
Also, I'm just throwing this out there, but what if my mom were to just move out of the house and stop paying the mortgage? I know her credit would take a hit and what not, but theoretically what would happen if she did this?

Summarize the given text in a few sentences.
<bot>: Dad passed away, mom wants to sell the house, but can't because my dad didn't write a will and the title can't be released without the consent of a son from his previous marriage