The youngest of four brothers with a potentially fatal illness is home following a second bone marrow transplant - after the first failed.
The failure of Luke's transplant has devastated the family
Luke Hartley, seven, and his brothers Daniel, 11, Nathan, 14, and Joshua, 16, from Romsey, Hampshire, were born with the genetic disorder, XLP.
The condition which attacks the immune system is often fatal.
Luke has returned home after a two-month stay over Christmas at Great Ormond Street Hospital in London.
His first transplant in May last year was unsuccessful because the donor cells failed to take.
Luke is the last of the siblings to undergo the procedure.
All were diagnosed in November 2003 with XLP - X-Linked Lymphoproliferative Syndrome, or Duncan's Syndrome.
Their parents, David and Allison Hartley, were told their sons were unlikely to reach their teenage years without a bone marrow transplant.
They set up a massive campaign for potential donors in 2004 with the Anthony Nolan Trust.
Joshua had his operation later that year after his mother was found to be a match.
Nathan and Daniel found donors as a result of the donor appeal.
XLP is one of the world's rarest fatal genetic disorders and is believed to affect only about 100 families.
Dr Paul Veys, clinical lead for bone marrow transplants at Great Ormond Street Hospital, said: "Never before have we successfully transplanted four members of the same family.
"This is certainly a first for our hospital and very possibly an international first. We're absolutely thrilled that all four boys are now back at home and doing so well."