The connection a boy has with his father shapes his life.
So when Simon Blackwell faced the prospect of losing his 14-year-old son to cancer he could already feel the pain of the milestones he would miss.
The first shave, beer, driving lesson, car and girlfriend – all of them looked unlikely as Deryn Blackwell battled the rare duo cancers Langerhans cell sarcoma and leukaemia.
And after bone marrow failed to graft after three failed transplants, the future looked bleaker still.
Mr Blackwell, who adopted Deryn in August 2012 after a long relationship with Deryn's mum Callie, said: 'There has been times when Deryn has said he just wants to die, and as a dad that's a very hard thing to hear.
'When you are worrying if your kid is going to get to his 16th birthday you realise what's important in life.
'I truly thought in a year's time I will be marking the anniversary of his death.
'As a dad it is important to mark land-marks in a boy's life, and I thought I had missed out on that.'
Deryn was diagnosed with leukaemia when he was just 10. Before that he was treated for autism and Tourette's syndrome.
Now he no longer has the two cancers, but he is fighting severe aplastic anaemia, where the bone marrow does not make enough blood cells for the body.
After leaving their Watton home a year ago to have the potentially life-saving treatment at Bristol Children's Hospital, mum Callie, brother Dylan and father have decided to live in the south west permanently.
Remarkably after being given just days to live in a hospice, the former Wayland Academy student started to grow his own bone marrow and is now starting to live a normal life.
'Knowing I am going to do those things fills me with relief, mixed with excitement and hope,' Mr Blackwell, a former weapons mechanic at RAF Marham, said.
'Deryn has a fighter's spirit now, his wicked smile is starting to come back, and he is back, the spirit is there again.
'What we have been through doesn't feel real. It feels like you're on TV. But Callie and I share a fierce positivity. Callie is at the forefront and I am her support.
'I do feel sad and depressed sometimes, but I don't want to do it too openly, because I don't want it to effect the family.
'And if you deal with every single complex emotion we wouldn't out one foot in front of the other.
'The way I deal with everything is to be as honest as possible.
'From day one I have never made a promise to the kids that I cannot keep, and that's become their safety net.'
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