Which English monarch married his brother's wife following his death?

Catherine of Aragon was born on the 16th December 1485 and was the youngest surviving child of the Spanish Catholic monarchs, Ferdinand II of Aragon and Isabella I of Castile. On the 14th November 1501 the 15 year old Catherine of Aragon married the 14 year old Arthur, Prince of Wales, son of King Henry VII, at St Paul’s Cathedral. The couple were then sent to Ludlow Castle in the Welsh Marches so that Arthur could begin his duties as Prince of Wales but within months both Catherine and Arthur became ill with what is thought to have been sweating sickness. Although it looked like both of them would die, Catherine recovered but only to find that Arthur had died on the 2nd April 1502.

King Henry VIII married his brother's widow in 1509. Catherine held firm to the fact that her first marriage was never consummated, though Henry would later use it against her in an attempt to annul their marriage so that he might marry Anne Boleyn.