The majority of US presidents have been either first-born children or first-born sons. Out of the first 44 presidents of the United States, 24 were first-born children or first-born sons, including Thomas Jefferson, Abraham Lincoln and Theodore Roosevelt. No US president has been an only child. It is thought that the reason why the majority of US presidents have been first-born children or first-born sons might be because oldest children tend to be given more responsibilities, such as babysitting their siblings, which might translate into the older children becoming comfortable with being leaders. First-born children might also have more confidence because they do not have to share attention with others as much during the first years of their lives, and their milestones are often more celebrated because they are the first in the family.
More about first-born children:
Out of the first 23 astronauts sent into space by the US National Aeronautics and Space Administration, 21 were first-born children.
Younger siblings typically earn better grades in school, even though first-born siblings tend to score higher on intelligence tests.
The first US president, George Washington, was not a first-born child. He had two older half-brothers, as well as three younger brothers and one younger sister.