Kate Middleton and Prince William are “going through hell” amid her cancer battle, claims their designer friend Amaia Arrieta.

Arrieta, who has styled the royal couple’s three children — Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6 — said she is devastated by the Princess of Wales’ diagnosis.

“I’m heartbroken at the moment, I think they are going through hell, I hope they will be back. It’s really personal,” she told the Telegraph.

Kate Middleton and Prince William are “going through hell” amid her cancer battle, claims their designer friend Amaia Arrieta.Getty Images

In March, Middleton, 42, aced that she had been diagnosed with cancer after staying out of the public eye for several months.

“In January, I underwent major abdominal surgery in London and at the time, it was thought that my condition was non-cancerous. The surgery was successful,” she said in an emotional video.

“However, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the early stages of that treatment.”

“I’m heartbroken at the moment, I think they are going through hell, I hope they will be back. It’s really personal,” she told the Telegraph.Getty Images

In March, Middleton announced that she had been diagnosed with cancer after staying out of the public eye for several months.BBC Studios

Middleton said the diagnosis has taken her and the Prince of Wales, 41, time to explain to their minor children.

“As I have said to them, I am well and getting stronger every day by focusing on the things that will help me heal, in my mind, body and spirits,” she added.

The princess also said that having William by her side has given her “a great source of comfort and reassurance.”

After sharing the heartbreaking news — which shut down conspiracy and cheating rumors — Middleton has reportedly been leaning on her parents and siblings for support.

The Princess of Wales said the diagnosis has taken her and William time to explain to their minor children.Getty Images

Earlier this month, William said his wife and children were “doing well.”PA Images via Getty Images

“While you certainly don’t see them photographed together very often, they are very much there in the background,” royal expert Katie Nicholl told Entertainment Tonight in March.

“They are absolutely fundamental.”

Earlier this month, William gave an update on how his wife and children were doing, saying everyone was “doing well.”