Barbara Sinatra, philanthropist and wife of singer Frank Sinatra, dies at 90

— -- Barbara Sinatra, the former model, activist and wife of the late singer Frank Sinatra, died Tuesday at her home in Rancho Mirage, California, according to a family spokesman. She was 90 years old.

The spokesman, in an official release from the Barbara Sinatra Children's Center, said she died of natural causes and was surrounded by friends and family at the time of her death.

Barbara Sinatra married the iconic singer in 1976 and they remained married until his death in 1998. She was Sinatra's fourth wife and had been married twice before herself.

"He was always very much a gentleman and he really cared about treating me well," Sinatra told the New York Times in 2011 about her famous husband.

But the Missouri native wasn't just a former model and the wife of a legendary singer. She helped found the Barbara Sinatra Children's Center in the 1980's to assist young victims of physical and sexual abuse.

"They can have a simple loving life that they didn't have before." Sinatra told CBS in 2013. "You feel like you're saving lives, and you are."

An official release today from her foundation stated, "Through Barbara Sinatra's efforts, more than 20,000 children through age 18 have received beneficial therapy at [the center], making it possible for them to cope with traumas associated with abuse."

Barbara is survived by her son Robert.