It was my brother Jonathan's birthday earlier this week. He would have been 51 had he not died in a cot death at seven months old. And while I never met him, he will always remain a big part of my life.

The story of that horrendous discovery one bleak November morning is a central part of our family narrative. And as the next sibling to be born, it inevitably shaped the way I was brought up, especially in my early years. His ashes have been kept in a birdbath that my mum and dad positioned in a prominent place in the garden whenever we moved house. Both literally and emotionally, he has always been around.

Even now, no one knows exactly why it happens. But the risk factors are well researched. Babies must be put to sleep on their backs not their fronts. Too many blankets can overheat a child. Bed sharing is a risk. And a house where parents smoke is a considerably more dangerous environment.

With the widespread dissemination of this information, sudden infant death syndrome had dropped dramatically in the past 25 years. Nonetheless, it remains the leading cause of postnatal mortality. In the UK, five children still die this way every week. As the newly rebranded Lullaby Trust (until earlier this month known by the more forbidding name of The Foundation for the Study of Infant Deaths) has recently shown, this remains a mother's greatest fear. Perhaps this is just stating the obvious; nonetheless, over half of new mums are not actually following sleep safety advice.

Other research is also fascinating, if inconclusive. A study in 2012 by the Metropolitan police has indicated that cot death is often more prominent in poorer areas. In London, for instance, the borough with the highest numbers of cot deaths is Southwark, where my parish is, and the areas with the lowest numbers are, generally speaking, in places of greater affluence. Yet it is also the case that some generally poorer parts of town, such as Tower Hamlets, have a relatively low rate of sudden infant death syndrome. It is difficult to know what all this means.

Much of this is not publicly talked about. It is often seen as too distressing. And tracking poverty and cot death is politically highly dangerous, not least where there is so much irresponsible rhetoric linking poverty and fecklessness currently in the air. Furthermore, we are often culturally far less confident at talking about personal tragedies such as cot death than we once were.

In a culture so saturated with upbeat positivity, the person who has experienced such an enormous weight of sadness as that which comes from losing a child is often avoided and ignored. Not out of cruelty, of course. It is just that people often do not know what to say.

As death becomes an increasingly less visible part of everyday life, we are losing the art of public consolation. My mother recalls acquaintances avoiding her eye in the street, clearly uncomfortable discussing so distressing a subject. I wouldn't want to upset her, goes the internal logic. And so the experience of losing a child is often accompanied by a crippling sense of social isolation.

We still speak about my brother. "Call me by my old familiar name, speak to me in the easy way you always used. Put no difference in your tone, wear no forced air of solemnity or sorrow," as Henry Scott Holland, a former canon of St Paul's Cathedral, once famously said in a sermon.

Jonathan would have been the good boy of our family, say my parents. Unlike his more bolshy younger siblings, he was much more easy going that the rest of us. It feels odd to miss someone that you have never met. But I do.

Twitter: @giles_fraser