It’s fair to say that King Charles’ second year as king didn’t go as planned. The monarch was forced to cancel a massive amount of royal duties due to his cancer treatments and, to this day, remains locked in a fight with the disease. Meanwhile, his beloved daughter-in-law, Kate Middleton, underwent the same challenging period, with their relationship reportedly growing stronger by the day.

If certain sources are to be believed, Charles sees Kate as the “daughter he never had,” and their relationship is stronger than ever. Still, one day, Kate is destined to take over from Camilla as queen. King Charles has seen both his mother, Queen Elizabeth II, and his wife in action, but it appears as if he won’t be giving his daughter-in-law any advice on what she might encounter when her husband takes the throne.

The king has given Kate advice throughout her time within the royal sphere, but when it comes to advice about how to act as queen, he won’t tell her anything. Why? Well, there’s a heartbreaking reason behind it.

King Charles and Kate Middleton have always had a very close relationship. When the Princess of Wales entered the royal fold for the first time, then-Prince Charles was impressed, and from there, their fondness for one another has been common knowledge. Kate has even been labeled “the daughter he never had,” and after what happened last year – when they both received cancer diagnoses – it appears they have grown even closer.

Royal expert Victoria Arbiter pointed out that Charles and Kate’s already strong relationship has likely grown more vital as they faced similar health struggles. Charles was diagnosed with cancer in early February, while Kate revealed her diagnosis last March.

Charles and Kate decided to step back from royal life to focus on treatment and recovery. Speaking on The Royal Beat, Arbiter said they “would have found tremendous comfort in each other, going through something so similar.”