According to Pink News, the UK parliament is trying to pass legislation that would allow a child born to an openly gay king or queen to be recognized as consort, and able to inherit the throne. This comes on the heels of Queen Elizabeth updating a century-old rule that will make the first child of William and Kate, if born a girl, a "princess" and not a "lady," and thus entitled to the throne. In the past, a male heir, even if younger than his sister, was ahead of her in the line of succession. Elizabeth became queen only because she has no brothers.
British Prime Minister David Cameron is pushing for the legalization of same-sex marriage in the UK, which would open the door for an openly gay monarch and the possibility of their offspring inheriting the crown. Before the amendment could be up for debate it would need to be backed by John Bercow, the speaker of Commons, which is likely, because he is a well-known supporter of queer rights.
A law allowing the gay marriage of a king or queen, and for their children to be able to inherit the throne, wouldn't be without obstacle, controversy and conflict of interest -- the ruling royal is the supreme governor of the Church of England, which opposes same-sex marriage.