Among the US Presidents, five surnames can be found that are each shared by two different men:
Adams: John Adams (the 2nd president); John Quncy Adams (6th)
Harrison: William Henry Harrison (9th); Benjamin Harrison (23rd)
Roosevelt: Theodore Roosevelt (26th); Franklin D. Roosevelt (32nd)
Bush: George H. W. Bush (41st); George W. Bush (43rd)
Johnson: Andrew Johnson (17th); Lyndon B. Johnson (36th)
John Adams was the father of John Quincy Adams.
William Henry Harrison was the grandfather of Benjamin Harrison.
Theodore Roosevelt and FDR were fifth cousins; FDR married Eleanor Roosevelt, TR’s niece.
George H. W. Bush was the father of George W. Bush.
Andrew Johnson and LBJ were not related.