Kate Middleton was very careful about how she and Prince William broke the news of her cancer diagnosis to their three children — Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5. In a video shared to their royal Instagram account on Friday, March 22, Kate revealed that after undergoing a major abdominal surgery in January, post-op tests revealed cancer had been present, leading her medical team to advise she have preventative chemotherapy. “I wanted to take this opportunity to say thank you personally for all the wonderful messages of support and understanding whilst I’ve been re…