[2] William's sister, Margaret Groesbeck, was married to his wife's brother, Robert Wallace Burnet.

[3] Through the marriage of his sister, Olivia Augusta Groesbeck, he was the brother-in-law of prominent Civil War general Joseph Hooker.

He served as member of the Peace Convention of 1861 held in Washington, D.C., in an effort to devise means to prevent the impending war.

In 1872, he was nominated for president of the United States by Liberal Republicans who were displeased with Horace Greeley, but his ticket was forgotten during the excitement of the campaign, at the end of which he received one electoral vote for vice-president.

[2] Groesbeck died in Cincinnati, Ohio, on July 7, 1897, and was interred in Spring Grove Cemetery.