Richard FitzWilliam, 6th Viscount FitzWilliam

He was the eldest son and heir of Richard FitzWilliam, 5th Viscount FitzWilliam by his wife Frances Shelley, a daughter of Sir John Shelley, 3rd Baronet and his first wife Bridget Nevill.

He was created a Knight Companion of the Order of the Bath (KB) in 1744 and was elected a Fellow of the Royal Society in 1747.

He lived for a time at Richmond Green in Surrey with his father-in-law Sir Matthew Decker, 1st Baronet, but later moved back to Mount Merrion, the family's principal seat near Dublin.

On 3 May 1744, he married Catherine Decker, eldest daughter and co-heiress of Sir Matthew Decker, 1st Baronet, a wealthy merchant of Dutch origin, by his wife Henrietta Watkins, at Sir Matthew's house in St James's Square.

[3] By Catherine he had issue including: Lord FitzWilliam died on 25 May 1776 at Mount Merrion and was buried at Donnybrook Cemetery.