Alfie Evans, the 23-month-old British toddler whose grave illness drew global attention, died early on Saturday, his family said.
Kate James and Tom Evans said their son's death overnight in Liverpool, England had left them "heartbroken".
The pope's tweets about the boy drew significant attention, prompting comparisons to Charlie Gard, a British baby who died a year ago despite his parents' fight - with the expressed support of Pope Francis and President Donald Trump - to keep him on life support.
After his death, family and supporters of Alfie Evans celebrated his life in pictures and hundreds of tearful supporters of Alfie Evans and his family gathered at a park near Alder Hey Children's Hospital to release balloons to honor the little boy after his death.
Purple and blue balloons scattered across the cloudy sky of Liverpool on Saturday as people chanted "Alfie, Alfie, AlfIe". "We loved you." In Alfie's final days, Tom Evans said he was working with doctors at the hospital to give his son "dignity and comfort" and thanked the staff "for their dignity and professionalism during what must be an incredibly hard time for them too". Trump has not mentioned Alfie's case.
"It's important to remember Alder Hey Hospital cared for Alfie not for two weeks or two months, but for 18 months, consulting with the world's top specialists - so its doctors' position that no further medical help could be given was very important", Nichols said Sunday, according to The Tablet. Gard died a day after being taken home, without the option of being put back on life support.
Charlie's parents subsequently failed to overturn his ruling in the High Court, Court of Appeal and Supreme Court in London. In such cases, the rights of the child take primacy over the parents' right to decide what's best for their daughters and sons. The court also ruled that the parents could not seek treatment for him elsewhere because further treatment would be against the child's best interests.
His parents gained support from the British public, where crowds showed up outside the hospital, and after Evans' death, offered messages of support via social media. "Today I pray especially for his parents, as God the Father receives him in his tender embrace", the pontiff wrote on his Twitter account.
Italian Foreign Minister Angelino Alfano tweeted on Saturday: "Goodbye, little Alfie".
The toddler, whose exact condition had not been diagnosed, is believed to have suffered from a DNA-related mitochondrial disease.
Doctors had removed Alfie's life-support following a High Court judge's ruling on Monday but he continued to live.
Alfie's doctors said he had an undiagnosed and untreatable neurological condition resulting in serious and irreparable brain damage.
Alder Hey Children's Hospital said staff had experienced "unprecedented personal abuse". The statement from Alfie's father was surprising given the animosity that had developed between the Evans family and the hospital. She says what happened to Alfie and his parents needs to never happen to get to any other child or patient. "This has been a devastating journey for them, and we would ask that their privacy and the privacy of staff at Alder Hey is respected". Alfie died three days later. He said flying Alfie to Italy could harm his health because, as court testimony indicated, the flight could trigger possible "continuous seizures due to stimulations" of the flight.