1. mom buys house outright 2. puts house in sister's name because she thought it would be best. 3. everyone undestood that the house was unofficially mom's. 4. mom and sister had a fight. 5. mom wants house back in her name and sister says no. 6. then on day sister says okay. 7. mom and sister sign the life estate and mom says she did not know what she was signing. 8. son comes into the picture.
Sis has no obligation, legally, to deed what is now HER house to anybody. If mom didn't want her to have it, she should have thought about that BEFORE putting the house in sis's name.
Under WHAT theory of law did mom think it is "BEST" to give away her house? It is NOT her house anymore- she only retains the right to live there.
Gee, heaven fordid people seek the services of an estate planning professional, or thoroughly research the implications themselves BEFORE they do this stuff.