April (?) 1153, William, count of Poitiers, first child of Eleanor and soon-to-be Henry II dies at the age of three years
April 1, 1204, Eleanor of Aquitaine dies
April 6, 1199. Richard the Lionheart dies of infected wound suffered at the siege of Châlus.
April 28 (?) 1539, Margaret Pole, countess of Salisbury, and last legitimate Plantagenets condemned to death by Henry VIII
For more on the demise of Richard.