Complex sentence: His maternal grandparents were William Ruthven, 1st Earl of Gowrie and Dorothea, a daughter of Henry Stewart, 1st Lord Methven and his second wife Janet Stewart.
Split into simpler sentences: His maternal grandparents were William Ruthven, 1st Earl of Gowrie. Dorothea a daughter of Henry Stewart, 1st Lord Methven and his second wife Janet Stewart.