Henry V, Count Palatine of the Rhine

Henry V, the Elder of Brunswick , a member of the House of Welf, was Count Palatine of the Rhine from 1195 until 1213.

After the death of his cousin Arthur I, Duke of Brittany in April 1203, Henry effectively became the heir of his maternal uncle John Lackland to the English throne, this ended though when Johns son was born in October 1207.

Source: Wikipedia