Elizabeth and Margaret (Freya Wilson, Ramona Marquez)
Bertie's daughters Elizabeth and Margaret don't show up in this movie much, but they're super fascinating—that little Elizabeth would grow up to become the Queen Elizabeth, the current Queen of England. She is the only major character from The King's Speech who's still alive, and it's amazing to think that she still has a living memory of her father (or grandfather, for that matter!).
And Elizabeth acts like a little girl who will one day be queen—she doesn't hesitate to give her father tough-but-fair feedback after his big wartime speech, saying,
ELIZABETH: Halting at first, but you got much better Papa.
Margaret, on the other hand, is much more praising when she simply says, "You were just splendid, Papa." Between the two of them, the girls also make up one of Bertie's biggest sources of motivation. He wants to be a good king so he can leave them a good world to live in.