Family and friends can never forget Stephen Ruggier – who would have turned 21 on October 24.
They plan to release 21 balloons by his grave and make the day a celebration of his life – cut short by the adult form of cot death.
The 17-year-old died in his sleep on October 4, 2004, and his family and friends lit candles in his memory on that date this year.
The former student at the Grange School in Christchurch was featured in campaigns by Cry (Cardiac Risk in the Young).
Mum Debbie, 41, from Southbourne, lives with husband Mark 41, and children Jack, 6 and Daniel 18.
She said: "The pain never gets any easier.
"If anything it becomes more real because at first you just don't really realise it has happened.
"It's hard. You miss them more and more and more.
"It will never get any easier. Never.
"I wrap myself in the other two boys. Stephen idolised Jack, so I look after Jack for Stephen. That's what keeps me going.
"We've told Jack that Stephen is in heaven, and he is going to write a letter to attach to a balloon.
"It's a very emotional time for Daniel with him just turning 18."
She added: "It's really great because his friends came around for the anniversary.
"One of them said they are still talking about him, and they always have a drink for Stephen – she said he will never be forgotten."
Debbie said Stephen would have been a mechanic by now – he loved cars from when he was playing with toys on the carpet as a child, to the course he had just started at Bournemouth College when he died.
The heart condition behind adult cot death could be genetic, so Stephen's family all needed testing with EGG monitors, but there were no problems.
Scientists are still studying what causes the irregularities behind the syndrome.
To contact Cry, call 01737 363 222.
