United Kingdom, May 24 -- The Princess of Wales' brother has opened up about their unique bond.

James Middleton, 38 - who has been open about his mental health issues - explained he has always relied on his family, including big sister Duchess Catherine, 43, to help him cope.

He told The Mirror: "I'm incredibly fortunate to have my two sisters, not just as siblings, but as friends.

"They've seen me at my best and at my lowest, and they've always been there when I've needed them.

"Sibling love is something unique, you can't choose your siblings, it can be complicated, it takes work, but when it's strong, I believe it's one of the most powerful bonds there is."

Speaking about his family, he went on: "They've always been emotionally ope...