Complex sentence: Her paternal grandparents were Garret Wesley, 1st Earl of Mornington, and Anne Hill, daughter of Arthur Hill-Trevor, 1st Viscount Dungannon.
Split into simpler sentences: Her paternal grandparents were Garret Wesley, 1st Earl of Mornington, and Anne Hill. Anne was a daughter of Arthur Hill-Trevor, 1st Viscount Dungannon.