James Middleton shared his support for his sister after the Princess of Wales released a major health update on Monday. Princess Kate shared a new video confirming she has completed her preventative chemotherapy treatment. She was diagnosed with cancer earlier this year and stepped back from royal duties to focus on her recovery. The Princess of Wales has only made two major public appearances this year, the first coming at Trooping the Colour and the second at Wimbledon alongside her sister Pippa and her daughter Princess Charlotte. Kate and James’s parents Michael and Carole Middleton featur…