willard – Member
May to December weddings were apparently quite common following the US Civil War, so there’s plenty of historical precedent.
From Wikipedia:
Maudie Hopkins (December 7, 1914 – August 17, 2008) was an American woman believed to be the last publicly known surviving widow of a Civil War veteran.
Born as Maudie Cecilia Acklin in Baxter County, Arkansas, she married William M. Cantrell (aged 86) on February 2, 1934, when she was 19. Cantrell had enlisted in the Confederate States Army at age 16 in Pikeville, Kentucky, and served in General Samuel G. French’s Battalion of the Virginia Infantry. He was captured in 1863, and was part of a prisoner exchange. He had had a previous wife, who died in 1929.