Archie Battersbee has died in hospital just hours after his life support was switched off on Saturday morning.
The 12-year-old schoolboy suffered a catastrophic brain injury in April.
His mum Hollie Dance announced that Archie died at 12.15pm on Saturday, outside the hospital where he was receiving treatment.
Speaking outside of the hospital, Hollie said she was "the proudest mum in the world".
Hollie told Sky News that Archie was "such a beautiful little boy and he fought right until the very end, and I am so proud to be his mum".
"He was taken off medication at 10am, his stats remained stable until two hours later when they removed the ventilation," said Ella Rose Carter, the fiancé of Archie's eldest brother Tom, speaking on behalf of the family.
"There is absolutely nothing dignified about watching a family member or a child suffocate.
"We hope no family has to go through what we have been through. It's barbaric."
Doctors told his parents that Archie was left brain-stem dead after the incident, and argued that continuing his life-support treatment was not in his best interests.
Judges refused to stop doctors from ending his care despite several court actions launched by Hollie and Archie's dad Paul Battersbee. In recent days during the legal battle, they made bids to the High Court, Court of Appeal and European Court of Human Rights to have him transferred to a hospice to die.
The pair, who are separated but both live in Southend, Essex, applied to the Court of Appeal on Friday after losing a High Court bid to have him moved to a hospice before his life-sustaining treatment was withdrawn.
Shortly after 6.30pm on the same day, the Court of Appeal confirmed that permission to appeal had been refused. No changes were made to Archie's care until all outstanding legal issues were resolved.
His parents were involved in a long-running legal battle over the withdrawal of treatment but this ultimately failed on Wednesday when the European Court of Human Rights refused to intervene in that initial battle.
After the ruling, Hollie and Paul shifted their focus to trying to get their son moved to a hospice and argued they should be able to decide where their son took his last breath. Their request was refused in a ruling at the High Court on Friday morning when Mrs Justice This concluded it was not in Archie's best interests to be moved.
In an interview with Sky News, recorded on Friday, Archie's mum Hollie said she was "pretty broken" and that the day had been "absolutely awful".
Breaking down, she said: "The last however many weeks since 7th April, I don't think there's been a day that hasn't been awful really."
Ms Dance added: "It's been really hard. Despite the hard strong face and appearance obviously in front of the cameras up until now, I've been pretty broken."
Asked if there was anything more she can do, Ms Dance said: "No. I've done everything that I promised my little boy I'd do. And I've done it."
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