General Notes

An undoubted Earl of Gloucester, perhaps the first authentic one, at any rate after the Conquest, is Robert FitzHamon's son-in-law, another Robert, who was an illegitimate son of Henry I and was so created 1122. The Earldom passed to his eldest son, William FitzRobert, and from him to John, later King John and husband from 1189 to 1199 (when he divorced her) of Isabel, the youngest of William FitzRobert's three daughters.  On John's coming to the throne the title did not merge in the Crown for it was not his in his own right but in right of his wife.

Isabel's situation now became that of a great heiress, for whoever she married next would gain the Earldom.  John prevented her taking a second husband at all for the time being, however, and exchanged the Earldom of Gloucester with Aumarie de Montfort, son of William FitzRobert's eldest daughter Mabel, for the Comte of Evereux, which he then used as a dowry to secure the marriage of his niece Blanche with the King of France's son.  Aumarie died childless and Isabel, who towards the end of John's reign married as her second husband Geoffrey de Mandeville, Earl of Essex and in right of his new wife now Earl of Gloucester too, died childless after marrying in the autumn of 1217 yet a third husband, Hubert de Burgh, Earl of Kent.

The latter seems not to have been recognised as Earl of Gloucester as well as of Kent, despite his wife's undoubted possession of the former Earldom by the time of their marriage.  But then she died only a few days later and her sister Amice, by now the only one of William FitzRobert's daughters still living, seems to have been recognised as Countess of Gloucester till her own death some seven and a half years later.  On the other hand Amice's son Gilbert de Clare, Earl of Hertford or of Clare (usually called the latter), was apparently acknowledged as Earl of Gloucester in addition to his other dignity from as soon as the month after his aunt Isabel's death back in 1217.  [Burke's Peerage]

3rd daughter of William FitzRobert.