Frank Sinatra's wife Barbara Sinatra dead at 90

Barbara Sinatra has died at the age of 90.

TMZ reports that the fourth and final wife of late singer Frank Sinatra passed away on Tuesday at her home in Rancho Mirage, Calif.

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Barbara reportedly "died comfortably surrounded by family and friends at her home" after months of declining health. Her funeral is scheduled for August 1.

Barbara married Frank in 1976, and they were married for almost 22 years before he passed away in 1998. It was the longest of Frank's four marriages.

See photos of Barbara Sinatra and Frank Sinatra together through the years:

31 PHOTOS
Frank and Barbara Sinatra through the years
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Frank and Barbara Sinatra through the years
Frank and Barbara Sinatra (Photo by ?? David Rubinger/CORBIS/Corbis via Getty Images)
American singer and actor Frank Sinatra and his wife Barbara. (Photo by Ira Wyman/Sygma via Getty Images)
NEW YORK, NY - CIRCA 1979: Frank Sinatra and Barbara Sinatra circa 1979 in New York City. (Photo by Sonia Moskowitz/IMAGES/Getty Images)
17th September 1978 (Photo by Daily Mirror/Mirrorpix/Mirrorpix via Getty Images)
Barbara Sinatra and Frank Sinatra (Photo by Ron Galella/WireImage)
Frank Sinatra and Barbara Marx (Photo by Ron Galella/WireImage)
Barbara Marx and Frank Sinatra (Photo by Ron Galella/WireImage)
OCTOBER 1971: Pop singer Frank Sinatra rides on a golf cart with Barbara Marx, whom he would later marry, at a celebrity golf tournament in October 1971. (Photo by Michael Ochs Archives/Getty Images)
NEW YORK, NY - CIRCA 1980: Frank Sinatra and Barbara Sinatra circa 1980 in New York City. (Photo by Sonia Moskowitz/IMAGES/Getty Images)
(Original Caption) 12/12/1979-Las Vegas, NV: Singer Dean Martin (R) announces the arrival of Frank Sinatra and his wife, Barbara, at a gala celebration at Ceasar's Palace to pay homage to the entertainer saluting his 40 years in show business and celebrating his 64th birthday. At left is Cary Grant and behind Martin is Milton Berle.
Frank Sinatra and Barbara Sinatra (Photo by Ron Galella/WireImage)
Barbara Marx and Frank Sinatra during Variety International Humanitarian Award Honoring Frank Sinatra at Century Plaza Hotel in Los Angeles, CA, United States. (Photo by Betty Galella/WireImage)
Barbara Marx, Frank Sinatra, Ronald Reagan and Nancy Reagan (Photo by Ron Galella/WireImage)
American singer and actor Frank Sinatra and his wife Barbara Sinatra arrive at the Red Cross Ball. (Photo by Elisabeth Andanson/Sygma via Getty Images)
Frank Sinatra amd Barbara Sinatra (Photo by Ron Galella/WireImage)
Monte-Carlo-15/08/84-Frank Sinatra and his wife, Barbara, attend the celebrity tennis tournament in Monaco. (Photo by Francis Apesteguy/Getty Images)
Frank Sinatra and Barbara Sinatra during Swifty Lazaar's Party For Billy Wilder at Mortimer's Restaurant in New York City, New York, United States. (Photo by Ron Galella/WireImage)
(2nd L-R) Frank Military, Frank Sinatra and wife Barbara Marx attend an event circa 1985 in New York City. (Photo by L. Busacca/WireImage)
Frank Sinatra and Barbara Marx (Photo by Ron Galella/WireImage)
Frank Sinatra and Barbara Sinatra during Friars Club Salute to Barbara and Frank Sinatra at Waldorf Hotel in New York City, New York, United States. (Photo by Ron Galella/WireImage)
LOS ANGELES - 1990: Singer Frank Sinatra and Barbara Sinatra pose for a portrait in 1990 in Los Angeles, California. (Photo by Harry Langdon/Getty Images)
March 1990: Full-length image of American actor and singer Frank Sinatra (1915 - 1998) posing with his fourth wife, Barbara Marx, outdoors at a White House State Dinner for Italian politician Giulio Andreotti, Washington, DC. Sinatra is wearing a tuxedo. Marx is wearing a long green gown. (Photo by Ron Sachs/Consolidated News Pictures/Getty Images)
Barbara Sinatra and Frank Sinatra during Martha Graham Dance Company Opening & After Party at City Center/Plaza Hotel in New York City, NY, United States. (Photo by Ron Galella, Ltd./WireImage)
Barbara Sinatra and Frank Sinatra during 'Society of Singers' - December 3, 1990 at Beverly Hilton Hotel in Beverly Hills, California, United States. (Photo by Ron Galella, Ltd./WireImage)
Quincy Jones, Barbara Sinatra, Frank Sinatra and guest (Photo by Ron Galella, Ltd./WireImage)
Barbara Sinatra and Frank Sinatra during 21st Annual Scopus Award Gala at Century Plaza Hotel in Century City, California, United States. (Photo by Ron Galella, Ltd./WireImage)
Singer and actor Frank Sinatra (1915 - 1998) with his wife Barbara, circa 1993. (Photo by Kypros/Getty Images)
Frank Sinatra and his wife Barbara celebrate his 80th birthday, New York, New York, November 30, 1995. (Photo by Allan Tannenbaum/Getty Images)
PALM SPRINGS - 1994: Personality Barbara Sinatra and Frank Sinattra for a portrait in 1994 in Palm Springss, California. (Photo by Harry Langdon/Getty Images)
LOS ANGELES, CA - NOVEMBER 19: Legendary American singer Frank Sinatra (1915-1998) poses with his wife Barbara for photographers shortly after a star studded event to honor his 80th birthday on November 19, 1995 at the Shrine Auditorium in Los Angeles, California. (Photo by Ron Davis/Getty Images)
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"Lady Blue Eyes," as she became known, established herself as a high-profile activist who dedicated her life towards combatting child abuse. With the help of her husband, Barbara opened the Barbara Sinatra Children's Center at Eisenhower Medical Center back in 1986.

"Since that time, over 20,000 children have received beneficial therapy here," Children's Center Director John Thoresen said in a statement. "There are several child advocacy centers like it around the country, [but] this one is probably most recognized."

The Frank Sinatra Celebrity Invitational Golf Tournament supported the center for decades. The event featured live performances by Frank from 1989 until 1995, but Barbara continued to throw fundraising events through 2016, the Desert Sun reports.

Barbara penned a revealing memoir in 2012 titled "Lady Blue Eyes: My Life With Frank Sinatra," which detailed their 22-year marriage.

"For a long time I had to pinch myself almost daily to believe that I, Barbara Ann Blakeley, the gangly kid in pigtails from the whistle-stop of Bosworth, Missouri, had somehow become the wife of Francis Albert Sinatra," she wrote. "Could I really be married to the singer whose voice I'd first heard at a drive-in when I was 15 years old?"

Barbara Sinatra is survived by her son Robert Marx.

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