From left, former first lady Barbara Bush, President George H.W. Bush, former president George W. Bush and former first lady Laura Bush holds hands during the invocationduring the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip)

Photo by: David J. Phillip

From left, former first lady Barbara Bush, President George H.W. Bush, former president George W. Bush and former first lady Laura Bush holds hands during the invocationduring the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip)