Burke’s Extinct Peers p. 101 says that he was the son of John Cantilupe and Margaret Mohun; this John was himself the third son of William Cantilupe and Millicent de Gournay.  Further it says that John his grandfather married Margaret dau and hr of William Cummin of Snitterfield.  To be investigated (Burke is not always to be believed).

Dec 2008, TFPL: Pat Junkin has asked a few questions about this John and caused me to look up Dugdale’s Warwickshire. pp. 504-5 where there is an enlargement of this tale of Burke’s.  Dugdale gives this tree:
                     N.N. Cumin
________________|________________
|                                                   |
William, Dominus de         Robert, yr brother
Snitenesfeld                                  |
_________________________________|
|                                        |
Walter Cumin,            John Cumin
hr to uncle William
= Margery
|
|______________________
|                                   |
Walter Cumin       William Cumin= Margery = William de Hastings
________________________________|
|
Margery, sole heir = John de Cantilupe
___________________|______
|                                        |
Walter de Cantilupe    John de Cantilupe
__________________________|__
|                                            |
Alienor = Thomas West      Sir John de Cantilupe
heir to   |___
bro. John     |
____________|____
|                          |
John West     Sir Thomas West

Dugdale gives various references to support this so it will be interesting to find how much these are thought to confirm this genealogy.
_________________________________________________

Dugdale in his Warwicks, p. 504: Three leopards heads jessant flower de lys, Or (tricked on p. 505).