Who was the legal grandson of the Earl of Merica?
Ealdgyth, daughter of Earl Ælfgar Ealdgyth ("fl. c". 1057–1066), also Aldgyth or in modern English, Edith, was a daughter of Ælfgar, Earl of Mercia, the wife of Gruffudd ap Llywelyn (d. 1063), ruler of all Wales, and later the wife and queen consort of Harold Godwineson, king of England in 1066. She was described by William of Jumièges as a considerable beauty.
Duchy of Cornwall The Duchy of Cornwall (Cornish: Duketh Kernow ) is one of two royal duchies in England, the other being the Duchy of Lancaster. The eldest son of the reigning British monarch inherits possession of the duchy and title of Duke of Cornwall at birth or when his parent succeeds to the throne, but may not sell assets for personal benefit and has limited rights and income as a minor. If the monarch has no male children, the rights and responsibilities of the duchy belong to The Crown and there is no duke. The current duke is Charles, Prince of Wales.