CBBC star Archie Lyndhurst, the son of Only Fools And Horses actor Nicholas Lyndhurst, died from a brain haemorrhage caused by a type of leukaemia, his mother has confirmed.
The 19-year-old died in his sleep at his home in Fulham, west London, on September 22.
Archie's mother, Lucy Lyndhurst, said a second post-mortem examination had revealed the haemorrhage was caused by a condition called Acute Lymphoblastic Lymphoma/Leukaemia.
In a post on Instagram, Mrs Lyndhurst wrote: "This is not Leukaemia as we know it, the word Acute in medical terms means rapid."
She added "there wasn't anything anyone could have done" as Archie had shown "no signs of illness".
The post described Archie as "the most extraordinary magical human being we have ever met", calling him "an old soul" and "incredibly advanced for his years".
She said her family's "world blew apart" following Archie's death, adding of the condition which killed him: "It's very rare and around only 800 people a year die from it."
The post went on to say: "We are so grateful and privileged to have been chosen to be his parents.
"The journey and adventure has been the best anyone could ever have wished for.
"A truly magical time in every way possible."
Mrs Lyndhurst said that just days earlier, her son had been celebrating his birthday with "the love of his life Nethra".
She added: "Life is fragile, precious and sometimes incredibly cruel."
Born in 2000, Archie is Rodney Trotter star Nicholas's son with his wife of 21 years, former ballet dancer Lucy Smith.
Archie followed his father into the profession, appearing in Jack Whitehall's Bad Education series and voicing a character in the video game Final Fantasy XIV: Heavensward.
He was best known for playing Ollie Coulton on comedy show So Awkward, which aired on CBBC.