1455 - Lady Margaret Beaufort married Edmund Tudor, 1st Earl of Richmond. They were the parents of King Henry VII, grandparents of King Henry VIII and great grandparents of King Edward VI, Queen Mary I and Queen Elizabeth I.
Edmund Tudor was the first child and eldest son of Owen Tudor. His mother was Catherine of Valois, Dowager Queen Consort of England. His parents' marriage was kept secret and was not common knowledge until after Catherine's death.
Without them there would have been no Tudor Dynasty.