Thomas FitzWilliam, 1st Viscount FitzWilliam Irish peer (1581–1650) Parents Sir Richard Fitzwilliam Jane Preston Children Richard Fitzwilliam William FitzWilliam, 3rd Viscount FitzWilliam Oliver FitzWilliam, 1st Earl of Tyrconnell Siblings Catharine Fitzwilliam Mary Fitzwilliam Partners Margaret Plunkett