Person:Margaret Plantagenet (5)

_____ de Warenne
b.Abt 1170 Surrey, England
 
m. Apr 1164
  1. Isabel de WarenneAbt 1154 - Bef 1234
  2. Geoffrey de WarrenAbt 1160 -
  3. William de Warenne, 5th Earl of Surrey1166 - 1240
  4. Suzanne de Warenne1166 -
  5. Maud de Warenne1168 - 1207
  6. _____ de WarenneAbt 1170 -
  7. Maria PlantagenetAbt 1175 -
  8. Ela de Warenne1176 -
  1. Richard FitzRoy _____Abt 1192 - 1246
Facts and Events
Name _____ de Warenne
Gender Female
Birth? Abt 1170 Surrey, England
Marriage to John of England

The chronicler known as "Robert of Gloucester" wrote that the mother of Richard FitzRoy was "the erles daughter of Wareine". There's no corroboration of this statement. Nor is there any record of Prince John having a liaison with a Warenne girl (who would have been a half first cousin). So it could easily be a mistake.

If we take it at face value, John's mistress is unlikely to have been Earl Hamelin's eldest daughter, Maud, who had a busy marital career. It's perhaps not impossible that she was unknown younger daughter who died unmarried and unrecorded. Otherwise the choice falls between the Earl's two known younger daughters, Isabel and Ela. Earlier writers favored Ela, but modern scholarship tends to favour Isabel.

References
  1.   daughter, in Cawley, Charles. Medieval Lands: A prosopography of medieval European noble and royal families.