James Middleton offered "unconditional" support to his sister Catherine, Princess of Wales during her battle with cancer

He told The Times newspaper: "What I think is that, as a family, you learn to see and process and understand things.

"For her and her family it was a challenging time, and I know for us and our bigger family it was a challenging time, but I think it's about communication and it's about offering support and help where you can.

"Being there for someone is such an important part, and it doesn't necessarily have to be on your terms and it shouldn't be on your terms.

"It should be on their terms; unconditional: 'I'm not doing it for something in return. I'm doing it because I love you.'

"And that's the simplest way of really demonstrating love. You can do it in all these various fancy ways but actually, you know, it is just generally being there."

Catherine confirmed she had finished her cancer treatment in September in a message posted on social media, which read: "As the summer comes to an end, I cannot tell you what a relief it is to have finally completed my chemotherapy treatment.

"The last nine months have been incredibly tough for us as a family."Life as you know it can change in an instant and we have had to find a way to navigate the stormy waters and road unknown."

James - who has been open about his own struggles with depression - previously revealed Catherine was able to rely on her relatives, as well as her husband Prince William and their three children, during the dark times.

He told Britain's HELLO! magazine: "We are certainly a close family that goes through things together.

"That was the experience I had through my challenges, and I certainly feel like it's something that her [Catherine's] family and our family are doing too."