How are we defining "out" for the Royal Family? Publicly announced by that person him/herself, or assumed or rumored?
It's often claimed that Edward II (1307-1327) was homosexual. And that several of his close male associates were his lovers. The future King's father, Edward I, at one point had the Prince's closest male friend exiled to France, for reasons that are unclear. He later returned, only to be executed by the English Barons a few years later. Who were struggling with Edward II for dominance, and later deposed the King in 1327.
These actions, and the contemporary references & rumors (one chronicle speaks of Edward II as a "sodomite"), could all be politically motivated. But they did exist. Meanwhile, the current Queen's cousin Lord Mountbatten has publicly declared himself to be gay, and that may be a first.
He's been married with children, BTW. Maybe he can meet the only bona-fide homosexual in the British Commonwealth, RJ's God-Said from Australia. Who contends only pure gays like himself who have never even dated a woman can really be homosexuals. All the others are bisexual or straight pretenders. Their discussion together would be interesting.