The original target of the Bryan-boosters was the William Bryan - Joan Fitzalan marriage, an obvious magnet. That didn't work - no issue - so they thought, Joan could have a daughter, by Etchingham, and the daughter could marry a Bryan. And hey, he could be William's nephew.
But then it turned out none of Lord Bryan's 3 known sons had any sons or could acquire any, so they gave Lord Bryan a 4th son. But they'd have needed to invent an extra generation. Instead of which, somewhere along the line, the son's wife Margaret got dated earlier and moved up a generation, so she was no longer a daughter of Joan Fitzalan, which lost the point of her being an Etchingham in the first place.