Motes died yesterday at Saint John's Health Center in Santa Monica, California, where she was being treated, sources close to the family said, reported the New York Post.
The news comes a little more than a year after it was learned that Roberts' half-sister, Nancy Motes, committed suicide.
Motes was living with her daughter, son-in-law and three grandchildren before her death. A request for comment from Roberts' representative was not immediately returned.