Who was the first predasent who was and only child?

The first U.S. president who was an only child was James Buchanan, the 15th president, serving from 1857 to 1861. He was born on April 23, 1791, in Pennsylvania and had no siblings. Buchanan's presidency is often noted for its challenges leading up to the Civil War. His status as an only child contributed to his solitary personality and his later life choices.