William Henry Harrison Sr 9th president of the USA is George Washington, 1st President of the United States' sister-in-law's husband's nephew!

George Washington, 1st President of the United States
 

→

Martha Washington, First Lady of the USA
his wife

→

Anna Maria Bassett
her sister

→

Hon. Col. Burwell Bassett
her husband

→

Elizabeth Harrison
his sister

→

William Henry Harrison Sr 9th president of the USA
her son