Billy Carter, registered foreign agent of the Libyan government and brother of President Jimmy, urinated in public at the Atlanta airport. Sam Houston Johnson, alcoholic and brother of President Lyndon, claimed he was virtually a hostage in the White House and was followed by the Secret Service when he went out. Donald Nixon, budding entrepreneur and brother of President Richard, used his fraternal connection in the late 1950s to secure a business loan. You can choose your friends, but not your family. A number of politicians have found the axiom all too true. Mrs. Clinton’s brothers may yet play a...