Brothers:
* Robert, Earl of Gloucester (illegitimate son of Henry I, half-brother of Henry II)
* William FitzEmpress (illegitimate son of Henry I, half-brother of Henry II)
* Geoffrey of Nantes (illegitimate son of Henry I, half-brother of Henry II)
Sisters:
* Matilda of England (daughter of Henry I, half-sister of Henry II)
* Mary of England (daughter of Henry I, half-sister of Henry II)
It's important to note that Henry II's half-siblings were all children of Henry I from different mothers. Henry II's mother was Matilda of Boulogne, and his father was Geoffrey V, Count of Anjou.