It was revealed recently by family barristers that Prince William stands to inherit the planet Mongo from the estate of Charles Middleton (AKA Emperor Ming the Merciless) great grandfather of his bride to be Kate Middleton.
A stipulation in his will states that if any of his lineage marries into royalty, the Kingdom of Mongo will pass to them.
Prince William refused to comment on this news pending review of Brittan's Space Program and other logistic matters involved in getting to Mongo whose orbit has not been tracked since the 1950's.
He did show a bit of a smile at our query.
Whether or not Ming's kingdom includes Mars which Emperor Ming also conquered in one episode is not clear at this hour.
It may be some time before all this is finalized and proper ceremonial reception of new kingdoms is worked out.
Whether Mongo will join the EU is not clear at this time.