Georgia girl writes heartbreaking letter to Santa

A 7-year-old Georgia girl wrote a heartbreaking letter to Santa this year, requesting that he cures cancer.

Allie Hart's brother, Robert, was diagnosed with Acute Lymphoblastic Leukemia in December of 2010. He's spent more than half his life, and Allie's entire life, undergoing chemotherapy and other treatments.

Over the last seven years, Robert has had over 65 spinal taps, around 800 doses of chemotherapy, about 16 days of radiation, three separate leukemia protocols, and two clinical trials.

"Robert is now 13-years-old and as innocent as they come," mother Kasie Hart said. "Still believes in Santa."

Robert's younger sister, Allie, also believes in Santa and is hoping for a Christmas miracle.

Mrs. Hart recently shared a photo on Facebook of a heartbreaking letter her daughter wrote to Santa, asking him to cure cancer.

The letter reads:

Kasie Hart said the letter was the sweetest and saddest thing she's ever read.

"Our kids deserve so much more," she said.

Allie was just 8-months-old when her brother was diagnosed with cancer.

"This little girl loves her brother so much," Hart previously said on social media.

Hart told FOX 5's Katie Muse her son is doing okay, and still fighting hard. Learn more about Robert the Great by visiting the following links:

DON'T MISS: Watch Robert transform into a superhero