Half-brother kings

Are there examples of kings of different countries who are half-brothers
through their mother having married two different kings? Are there any
examples of three or more half-siblings who are sovereigns of any degree?
I'm not talking about merely deferring succession from an older child for
the sake of keeping realms or titles separate.

sionevar...

How about the sons of Emma of Normandy? Her first husband was King Ethelred
the Unready of England, with whom she had King Edward the Confessor of
England. Her second husband was King Canute of England and Denmark, with
whom she had King Harthacanute of England and Denmark.

Tom Wilding / Stephen Stillwell...

She also had a stepson - a son of Canute's first wife who was also King.
That admittedly is half-sibling through a father rather than a mother.

Also, can anyone think of any other interesting scenarios involving
relations of the half-blood, including having a genealogical rival/claimant
as the half-sibling to a king, etc.

mjcar...

How about Fulk of Anjou, who married secondly Melisende, Queen of
Jerusalem? His son Geoffrey, by the first marriage, succeeded as Count
of Anjou (and was father of England's King Henry II) while his sons by
the second marriage, Baldwin III and Amaury I, succeeded in turn to
Jerusalem.

Charles von Hamm