Born: c. 1524/1526, Died: 1569/1596
Known for: Possibly being the illegitimate children of Henry VIII; Catherine was lady-in-waiting for Henry's fourth wife, Anne of Cleves. (Source)
Mary has two children with Henry VIII, making each of them half royal. That doesn't mean that Mary loves them halfway, though: she cares for them immensely, and she will do anything for them.
We don't really get to see little Henry as a character, but we do watch young Catherine grow and change. As yet another Boleyn girl, Catherine quickly becomes a pawn in Anne's plots. You've seen the meme that says 9 out of 10 children get their awesomeness from their aunt, right? Catherine is that 10th out of 10 child: she's all Mary, all the way. She has none of Anne's conniving nature, which is why Anne takes her at the end. Mary has abandoned her, and Catherine acts as a Mary surrogate, a little bit of sanity in Anne's insane world.
Catherine sweetly keeps Anne company in the Tower of London until Anne is executed. When she returns to Mary, Mary flees the court for the country, not wanting her daughter to repeat her own mistakes.