Logan Stevenson was born with a rare genetic disorder, Fanconi anaemia that often leads to cancer.
"I held him all day he was comfortable with his medication then at 8:18 my son took his last breath in my arms Logan passed away im so sad upset and im in disbelief he is with angels and he's in no more pain," Logan's mother Christine Swidorsky said in a post on her Facebook page.
"No more sickness no more hospitals. We love all of u for all your prayers thank u all for caring god bless u all! And most of all god bless Logan I'll c u in my dreams my son," she was quoted as saying by Pittsburgh Post-Gazette.
Doctors said on July 26 that Logan Stevenson has one to two weeks left to live.
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Logan has been in and out of hospitals since he was born on October 22, 2010, weighing just 3 pounds.
Logan had also lost a kidney to a tumour. His once big, beautiful curls are no longer atop his head.
Logan's story was picked up across the world.