Which preposition to use with groomsman

to Occurrences 3%

" A few more questions and answers, and the gentlemen, exchanging friendly adieus, pursued each his own course; Sir Owen Ap Rice pushing forward for Cheltenham, and the Earl of Pendennyss proceeding to act as groomsman to his cousin.

as Occurrences 1%

Jane and Emily acted as bridesmaids to their sister, and as both the former and her mother had insisted there should be two groomsmen as a counterpoise, John was empowered with a carte-blanche to make a provision accordingly.

of Occurrences 1%

Maltboy, who, being one of the appointed groomsmen of the day, was in extraordinary spirits, was profuse in his congratulations to Uncle Ith, and insisted, rather unnecessarily, upon introducing him to the retired merchants and the bachelor Bank President.

Which preposition to use with  groomsman