Former U.S. presidents George W. Bush (C) and his father George H.W. Bush laugh alongside former first ladies Laura Bush (R) and Barbara Bush (L) during the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013.
Former U.S. President George H.W. Bush participates in the coin toss ahead of the start of Super Bowl LI between the New England Patriots and the Atlanta Falcons as former first lady Barbara Bush looks on in Houston , Texas, February 5, 2017.
First Lady Michelle Obama (L) poses with former first ladies (2nd L-R) Laura Bush, Hillary Clinton, Barbara Bush and Rosalynn Carter as they attend the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013.
George W. Bush is shown with his father, future President George Bush and mother, future first lady Barbara Bush in Rye, New York, in this file photo taken during the summer of 1955. REUTERS/File Photo
Future first lady Barbara Bush holds son George W. Bush as the future President George Bush looks on in New Haven, Connecticut, in this April 1947 photo. REUTERS/File Photo
George W. Bush with his mother Barbara Bush, father, George Bush, and grandparents, Prescott and Dorothy Bush in Midland, Texas. REUTERS/File Photo
Portrait of the Bush family sitting in front of their home in Kennebunkport, Maine, August 24, 1986. REUTERS/File Photo
Barbara Bush pets her dog Millie while waiting with her granddaughter Barbara for President George H.W. Bush to arrive on the White House steps in this undated photo in Washington, D.C. REUTERS/Rick Wilking
A Bush family portrait in Houston, Texas, July 22, 2000. REUTERS/File Photo
Bush family members pose for a group portrait before celebrating their parents' birthdays, in Houston, Texas, June 10, 1999. REUTERS/File Photo
Former U.S. President George H.W. Bush raises hands with his wife, former first lady Barbara Bush as they await the start of the Republican presidential candidates debate sponsored by CNN in Houston, Texas, February 25, 2016. REUTERS/Mike Stone
Barbara Bush (C) speaks as her son, Republican presidential candidate Jeb Bush (R) looks on during a campaign event in Spartanburg, South Carolina February 19, 2016. REUTERS/Rainier Ehrhardt
President Barack Obama laughs alongside former first lady Barbara Bush during the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013. REUTERS/Jason Reed
Former first lady Barbara Bush (L) and first lady Michelle Obama walk into an event honoring the 5,000th winner of the "Daily Point of Light" award in the East Room of the White House in Washington July 15, 2013. REUTERS/Larry Downing
Republican presidential candidate Mitt Romney (L) picks up the formal endorsement of former President George H.W. Bush and former first lady Barbara Bush in Houston March 29, 2012. REUTERS/Donna Carson
Former first lady Barbara Bush speaks during a news conference with Republican presidential candidate Mitt Romney and former President George H.W. Bush as Romney picks up their formal endorsements in Houston March 29, 2012. REUTERS/Donna Carson
Former U.S. first lady Barbara Bush listens to her son, President George W. Bush, as he speaks at an event on social security reform in Orlando, Florida, March 18, 2005. REUTERS/Jason Reed
(L-R) Prince Charles, Princess Diana greet Vice President George Bush and Barbara Bush during dinner at reception at the British Embassy hosted by Lady Wright, in Washington, D.C., November 10, 1985. REUTERS/Chas Cancellare
Michael Jackson (L) and first lady Barbara Bush walk near the Rose Garden at the White House in this 1980s file photo. REUTERS/Rick Wilking/Files
Former first ladies (L-R) Barbara Bush, Johnson, Betty Ford and Nancy Reagan pose at the Botanic Garden Conservatory in Washington, May 11, 1994. REUTERS/Mannie Garcia
Barbara Bush gestures during a photo shoot with celebrities at a party in Los Angeles, California, in this undated photo. Top row, L-R; Tom Selleck, Arnold Schwarzenegger, James Woods and Roger Moore. Middle row, L-R; Frank Sinatra, George H.W.
Vice President George Bush and his wife Barbara with Pope John Paul II during an audience at the Vatican, June 24, 1985. REUTERS/Luciano Mellace
President Ronald Reagan (2nd L) and Vice President George Bush, (2nd R), accompanied by wives Nancy (L) and Barbara, join hands after the President endorses the Bushes' run for the presidency during the President's Dinner in Washington, D.C.
German Chancellor Angela Merkel (L) talks to former President George Bush (R) and her wife Barbara (C) as they attend a ceremony of the Konrad-Adenauer foundation to mark the upcoming 20-year anniversary, in November, of the fall of the wall which
President George W. Bush (R) waves alongside his parents, former President George Bush and former first lady Barbara Bush upon their arrival Fort Hood, Texas, April 8, 2007. REUTERS/Jason Reed
Barbara Bush is pictured with George H.W. Bush during a presidential vacation in Kennebunkport, Maine, in this undated photo. REUTERS/Rick Wilking
Former first lady Barbara Bush listens to remarks during the christening ceremony of the USS George H.W. Bush at Northrop-Grumman's shipyard in Newport News, Virginia October 7, 2006. REUTERS/Kevin Lamarque
Former President George H. W. Bush and his wife Barbara Bush talk to the media in front of the restored childhood home of President George W. Bush after dedication ceremonies in Midland, Texas, April 11, 2006.
Former President George H.W. Bush (R) and his wife Barbara Bush (L) are seen kissing on a giant electronic screen in center field showing the "Kiss Cam" during the middle of the sixth inning in Game 4 between the Houston Astros and the St.
Barbara Bush is seen before game five of the 2017 World Series between the Los Angeles Dodgers and the Houston Astros at Minute Maid Park in Houston, Texas, October 29, 2017. David J. Phillip/Pool Photo via USA TODAY Sports
Former first lady Barbara Bush throws out the ceremonial first pitch to start Game 4 of the National League Championship Series, between the Houston Astros and the St. Louis Cardinals in Houston, Texas, October 17, 2004. REUTERS/Robert Galbraith
Former President George H.W. Bush gives a thumbs up with his wife Barbara at his side, after a successful parachute jump from approximately 12,500 feet at the U.S. Army Yuma Proving Ground, March 25, 1997. REUTERS/File Photo
Former first lady Barbara Bush tells the crowd to hush as she introduces her son President George W. Bush at an event in Orlando, March 18, 2005, REUTERS/Jason Reed
Former first lady Barbara Bush waves to fans as she walks on the field with former presidents George Bush and Bill Clinton before Super Bowl XXXIX in Jacksonville, February 6, 2005. REUTERS/Marc Serota
President George W. Bush watches returns from the presidential election with his family at the White House, November 2, 2004. REUTERS/Jason Reed
Barbara Bush speaks at the Waldorf Astoria hotel in New York on August 30, 2004, during the Republican National Convention's "W Stands for Women" rally. The group reminded party faithful of President George W. Bush's record for women's rights.
Barbara Bush acknowledges the cheers from the crowd as she speaks before the Republican National Convention in Philadelphia, August 1, 2000. REUTERS/File Photo
The parents of Texas Gov. George W. Bush, former President George H.W. Bush and his wife Barbara, react as their son came out on stage to accept the presidential nomination of the Republican party in Philadelphia, August 3, 2000.
Gov. George W. Bush gives his mother Barbara Bush a hug after a family portrait session in Houston, Texas, June 10, 1999. REUTERS/Adrees Latif