Complex sentence: William was also said to have descended from both Ivo de Taillebois and Eldred of Workington, contemporaries of William Rufus, but the exact nature of the relationship is unclear and indeed controversial.
Split into simpler sentences: William was also said to have descended from both Ivo de Taillebois and Eldred of Workington, who were contemporaries of William Rufus. But the exact nature of the relationship is unclear and indeed controversial.