Married Mary Kennedy.
Richard FitzGerald and Mary Kennedy are listed as parents on the baptismal record of Edward the engraver (1758 - 1834) at St Michan's RC in Dublin.
He was contemperary with the Hon Richard Fitzgerald, brother of the 19th Earl of Kildare (and therefore son of 18th Earl of Kildare). Although our Richard was himself a descendant of the Earls of Kildare (and therefore related to the Dukes of Leinster), as Roman Catholics his family would have had to be estranged from James the 1st Duke of Leinster, who, when this English title was invented in 1766, would have been required to be of a 100% protestant family or lose his rights to the title.