Barbara Sinatra, Singer's Widow and Philanthropist, Dead at 90

Frank Sinatra's widow remained actively involved with the couple's Barbara Sinatra Children's Center

Barbara Sinatra, the widow of Frank Sinatra, died at her home in Rancho Mirage, California, on Tuesday. She was 90.

John E. Thoresen, the director of the Barbara Sinatra Children's Center, first announced Barbara's death, noting that she was surrounded by family and friends at the time of her death. Thoresen told CNN that Sinatra died of natural causes.

The former model and Las Vegas showgirl was a devoted philanthropist in the later years of her life, founding the Children's Center together with her husband in 1986. The Barbara Sinatra Children's Center is a nonprofit that provides services for abused, neglected and at-risk children, and has treated more than 20,000 children at the center, with hundreds of thousands more being helped internationally via videos.

Born in Bosworth, Mo., on March 10, 1927, Barbara moved to Long Beach, California, with her family in the 1950s and was known as a Palm Springs socialite when she married Frank in 1976. At the time that they first met, Barbara was married to her second husband, Zeppo Marx, a former member of the Marx Brothers comedy team, and the singer was married to his second wife, Ava Gardner.

In her 2011 book, Lady Blue Eyes: My Life with Frank, Sinatra remembered that she first met Frank when she was asked to be a doubles partner with Gardner. In recent years, she opened up to the New York Times about the fact that her husband always remained friendly with his ex-wives.

"A very wise French lady once said to me, 'You never worry about old flames. You worry about new ones,'" she said.

When she and Frank eventually married in 1976, their union became the most enduring one for both of them; they were married until his sudden heart attack and death in 1998.

"Frank would come over and sit and read to the kids," Thoresen said. "But the best way she used Frank was she would say, 'I need a half-million dollars for this, so you do a concert and I get half the money.'"

In March, the Children's Hospital Los Angeles partnered with the center to raise $250,000 for services for children and their families to receive treatment at both facilities.

Barbara is survived by a son, Robert Oliver Marx, and a granddaughter.