In the sibling department, every President has had, at minimum, one half-brother or half-sister. However, a few Presidents are sometimes considered to have been raised as only children — most notably Franklin D. Roosevelt, whose only half-sibling (his father’s oldest son, James) was 28 years FDR’s senior. Bill Clinton’s half-brother, Roger, is about a decade younger than him. Barack Obama also has a 10-year age gap with his younger half-sister Maya, although he learned later in life that he possessed at least five more half-siblings on his father’s side. Meanwhile, Gerald Ford is the only child his mother and father produced, but he was raised with three younger half-brothers after his mother remarried, and as a teen, learned that he also had three younger half-sisters, via his father.
The no-only-children rule isn’t the only presidential birth quirk. Fifteen Presidents, including Joe Biden, are firstborns. Just seven occupants of the Oval Office have been the babies of their families, among them Andrew Jackson and Ronald Reagan. That means 23 Presidents have fallen somewhere in the middle of the birth order, with the likes of Grover Cleveland and Herbert Hoover being true middle children (they were born to families with nine and three offspring, respectively). John Tyler, the 10th President, fathered the most youngsters himself: 15.