https://groups.google.com/g/soc.genealogy.medieval/c/CpsI6xVuI3A/m/-S9AWF7HFu4J
The strong possibility that Clarice, wife of Sir Adam de Everingham, was a daughter of Roger la Warre and Clarice de Tregoz exists based on the following:

1. As noted by others of the list who have commented on this observation, Clarice or Clarissa was a relatively rare name amongst the upper strata of society.

2. The marriage of Clarice de Tregoz (1276 or before) runs well with the probable birth date of Clarice, wife of Sir Adam: given his birth date of 29 Aug 1279, his wife Clarice was probably born between 1279 and 1290. Their eldest son Adam de Everingham was born ca. 1307 according to CP.

3. There were daughters of the marriage of Roger la Warre and Clarice de Tregoz. In Knights of Edward I, Vol. V (Harl. Soc. series, Vol. 84), the record of Sir Roger la Warre names only his sons John and Roger, but does state (p. 158):

' Going to Gascony for K[ing Edward] he has grant that if he die there, leaving his heir a minor, his Exors. may hold Wykewarre Manor, Glou., and Brustlyngton Manor, Som., during such minority, and apply the revenues for marriage of his daughters, 9 Nov. 1295.'

4. There are IGI records of two individuals named Clarice la Warre, one born either 1278 or 1279 [no spouse indicated] and another born 'abt 1298'. The latter is shown in LDS Ancestral Files as the daughter of Roger la Warre and Clarice de Tregoz, and married to Roger Savage ca. 1324 - this individual is (not proven but) more likely to have been a daughter of John la Warre, 2nd Lord la Warre who m. aft 19 Nov 1294 Joan de Grelle.

[5] An additional piece of supporting evidence for this relationship is found in Vol. I, Knights of Edward I (Harleian series, Vol. 80, 1929). On p. 319, for Sir Adam de Everingham, it states:

' He owes 400 m. in Lincs., Yorks. and Notts., to his d. Sibyl, 2 Jy. 1320 (C.R.). '

Sibyl was the name of the sister of Clarice de Tregoz, wife of Sir Roger la Warre. The introduction of this name into the Everingham family appears to have been the result of the marriage of Sir Adam de Everingham to Clarice la Warre, whose daughter Sibyl would be a great-niece of Sibyl de Tregoz according to this theory.