After years of enormous power and political influence, no member of the Bush family currently holds political office. But as the focus on military action in Syria drags former President George W. Bush’s Iraq war policy back into the spotlight, the Bush family is quietly but forcefully gearing up for another, still-developing debate: The fight on Capitol Hill over a broad overhaul of the nation’s immigration laws—a discussion critical to protecting the Bushes’ legacy on what has, for decades, been a defining issue for them. … For the Bushes, immigration is deeply personal. The family chose to root its political...