Prince William’s “second mum” brings a “sense of normality” for the prince during Kate’s cancer treatment, a source has claimed. The prince’s mother-in-law, Carole Middleton, has been on hand to support the family during Princess Kate’s health troubles. A source has spoken about the multi-millionaire businesswoman’s relationship with the future King after they were spotted at a Norfolk pub together this week. The Prince of Wales was seen with Carole Middleton during a “low-key” visit to the pub in North Norfolk. The insiders told The Sun that Carole has “acted as a second mum to William bringi…