How Pierce works it.
"From the foregoing... it will be seen that Peter Percy* was son of Ralph Percy"
* see note page 18
This note gives us a long rigmarole about the Percys of Worcester, with a sentence tacked on:
"John Percy of Newton-on-the-Sea was, according to Brydges' Collins, brother of Peter Percy and the son of Sir Ralph Percy of the text."
This is the only mention we've had of Peter.
Brydges' Collins has 150 pages on Percys without any roadmap. But John is on page 287
which makes him the grandson not son of Sir Ralph. Ralph (p. 282) has 3 sons, Henry, Ralph and George, and John is the only son of Henry. No Peter.
So Pierce is perfectly honest - he points us to the source that contradicts his claim and breaks his pedigree, if we have the stamina.