I untied them once, years ago, but then there was a merge and they were tied in knots again.
But now I have no idea if I untied them right in the first place.
I posted links to threads in the gen-medieval archive, but Ancestry has broken them all. The dates were June 2000 and December 2006.
Richardson's Royal Ancestry 2013 vol 5 p 442 says only
Ela Brewes m Sir William Yelverton KB (prob b abt 1400) as his 2nd wife and they had
- one son, William esq, m Katherine Rands
- 3 daughters, Anne, Margaret (m Thomas Tyndall), Eleanor (m John Conyers).
Does not mention who Sir William's 1st wife was or what kids they had. Very cagey. He does call William esq "son and heir", which if correct would imply no extant sons from the 1st marriage.
There are prospective Magna Carta project trails through here.