King Charles treats Princess Kate like the “daughter he’s never had” amid their cancer battles, a royal insider claimed. The Princess of Wales’s bond with her father-in-law has grown stronger during their recent health scares. On Friday, Kate, 42, revealed via video she had been diagnosed with cancer and was undergoing preventative chemotherapy. This came after weeks of speculation and conspiracy theories regarding Kate’s whereabouts online. In February, Buckingham Palace announced that the monarch, 75, had been diagnosed with a form of cancer. The cancer was found during an operation to treat…