Sarah McKean heiratete 1798 den damaligen spanischen Gesandten in Washington und späteren dreimaligen Staatsminister Carlos Martínez de Irujo y Tacón. ###>Mckean's daughter Sarah married Spanish diplomat Carlos Martínez de Irujo, 1st Marquis of Casa Irujo, their son Carlos Martínez de Irujo y McKean, would later become Prime Minister of Spain.