I never understood why the clones refer to her as their queen, and I've sense how she reacts negativly to it. But seeing how great her kingdom has become, she can tbe given any title she wants; Thomas
Xion is a keyblade wielder, and a replica of Roxas.
Thomas first met Xion when he traveled to another dimmension, where this Xion was under the full control of Xemnas. However she perished during the conflict
During 10 new keys, what remained of both Xions, one in the main universe, the other in the neo universe, merged into a whole Xion, with memories from both. She freed the clone troopers from Sidious's control, and led them to settle on a new world, Clone Planet. Only a few, such as Roxas, Namine, Thomas, Tonto and Dani, know the planets location. The clones call her Queen Xion, a title she can't shake off.
3 years after 10 new keys, Sora accidently created Rion, the cloned son of Roxas and Xion, by playing with Tonto's cloner. Xion recieved the baby soon after, and raised him. Namine and Roxas are aware of this, as well as everyone else. Both Xion, Rion and their clone subjects particapte heavily in the conflict with Kronos.