James Middleton, 37, gave a “rare” interview where the author of Meet Ella: The Dog Who Saved My Life showered praise on his elder sister, Kate, Princess of Wales, 42, who recently beat cancer. “Catherine is very much on a public stage, and I’m in awe of a lot of the things she does,” James told Us Weekly. “I think the thing I’m most proud of is that she’s still the same person that I grew up with.” The Princess of Wales will one day be the author’s Queen, and James and Pippa Middleton couldn’t help but show their excitement about that possibility when Kate told them Prince William proposed in…