He married after becoming President at age 49 to someone who was 21. Only Prez to get married in the White House.
She was the daughter of Grover's work associate (Grover knew her from when she was a baby) and when that person died in a buggy accident when she was 11, he took over for the administrator for that estate, met with her often and showered her with gifts including her own horse and buggy. He was the Beast of Buffalo, and she was the Beauty. Thus the original Beauty and the Beast.

Another fun fact - their first daughter was named Ruth and she had the nickname Baby Ruth to which the candy bar company claimed they named it after her in order to avoid having to pay any royalty rights to George Herman "Babe" Ruth.