Hugh O'Neill, 1st Baron Rathcavan, was the youngest son of the second Baron O'Neill, while Terence O'Neill, Baron O'Neill of the Maine, Prime Minister of Northern Ireland, was the youngest brother of the third Baron.
Hugh O'Neill was the youngest son of the second Baron O'Neill. Terence O'Neill was the youngest brother of the third Baron. Terence O'Neill was Baron O'Neill of the Maine, Prime Minister of Northern Ireland. Hugh O'Neill was 1st Baron Rathcavan.