A 16th-century FitzWilliam of Sprotborough pedigree started with the usual hero of Hastings and married his son to a daughter of Warenne. The timescale is too stretched to guess which Warenne, but an early one obviously.
This was all junk, but surprisingly the Warenne marriage resurfaced in later versions, and now Ela's father was Hamelin, half-brother of Henry II.
The odd thing is that Ela is now shown as the widow of one Robert de Newburn, of whom nothing is known. Which kind of gives the impression that you couldn't make it up - unless it's very clever and that's what you're supposed to think.
Some versions make her the same daughter who had a fling with Prince John.
The Warennes had Conisbrough and Wakefield. Hamelin supposedly built Conisbrough Castle. The FitzWilliams were neighbours of Conisbrough at Sprotborough, and tenants of Wakefield at Emley, so it's not totally far-fetched. Emley could have been the wedding present - the FitzWilliams had it soon afterwards, they aren't known to have had it earlier, and there's no other obvious reason why they might have been given it.
But no actual primary source seems to exist.