Mary and a daughter named Mary. His mother was named Elizabeth, his mother-in-law was named Elizabeth, and he had a daughter named Elizabeth. His father was named Henry, he was named Henry, and he had two sons named Henry (one of whom died in infancy). So, as you can see, it becomes very difficult to distinguish the characters without a lot of awkward introduction every time the character is mentioned.
As a result, I decided to differentiate the names as much as possible.
Henry's first wife is referred to as Katharine of Aragon, as her name is spelled on her tomb. Katharine herself spelled it a variety of ways, but almost always with a "K" instead of the "C" most writers use.
Henry's sister is referred to as Mary Brandon, though she wouldn't have used that name in life. She preferred to be called Mary, Queen of France. She might have used "Mary Suffolk" because nobility usually referred to themselves by their title, not their surname. I decided to make it easier on the reader because her husband is referred to as Charles Brandon when he is mentioned, the name used most often in books about the Tudor era.
Henry's fourth wife doesn't play a role in Under These Restless Skies, but I mentioned her in the notes. She is referred to as Anna von Kleefes. She generally signed herself "Anna Daughter of Kleefes."
Henry's fifth wife is Katheryn Howard, as she herself spelled her name in her famous letter to Thomas Culpepper.
Henry's sixth and final queen is Kateryn Parr, how the lady spelled her own name on documents.