Lady Mary O'Brien Peerage person ID=26125 (1681–1780) Parents Mary Villiers William O'Brien, 3rd Earl of Inchiquin Children William FitzGerald Mary FitzGerald Lady Margaretta FitzGerald Anne FitzGerald James FitzGerald, 1st Duke of Leinster Elizabeth FitzGerald Frances FitzGerald George FitzGerald Henrietta FitzGerald Catherine FitzGerald Richard Fitzgerald Siblings William O'Brien, 4th Earl of Inchiquin Lady Henrietta O'Brien Charles O'Brien James O'Brien Partners Robert FitzGerald, 19th Earl of Kildare