Who was the legal grandson of the Earl of Merica?
Ealdgyth, daughter of Earl Ælfgar: Ealdgyth ("fl. Ealdgyth, daughter of Earl Ælfgar:  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. Ælfgar, Earl of Mercia: Ælfgar (died c. 1060) was the son of Leofric, Earl of Mercia, by his famous mother Godgifu (Lady Godiva).
Gruffudd ap Llywelyn