The relationship of cousins can be special, a bond forged in childhood to last a lifetime. I spent part of every school holiday with my cousins and stayed in touch with them in adult life.

Having a girl cousin of my own age made a welcome change from my brothers, one older, one younger; it was like having a sister without the competition for parental affection that occurs between siblings. Children usually squabble with their siblings but cousins don’t see each other often enough and can enjoy each other’s company on an easy-going basis.

When friendships develop between cousins, they usually endure. Schoolfriends can be fickle, causing much anguish, but a cousin is always a cousin. Even when there is little else in common, shared genes seem to generate affection. The relationship is particularly important for only children: an older cousin to hero-worship; a younger one to impress — a surrogate brother or sister.

Cousins can’t always be expected to like each other. One child remembers a miserable week spent with her cousin who also had a schoolfriend staying. The schoolmates ignored her, excluding her from all their games. Another narrowly missed causing GBH to his infuriating cousin with a croquet mallet. Only the fact that she could run faster than him saved her.

Parents, much as they would like to relax when their child has a cousin to play with, must make sure that nobody gets hurt emotionally or physically. Even when cousins get on well, vigilance may be needed. “Playing quietly upstairs” can mean painting each other blue for a game of Ancient Britons or giving the dog a new hairstyle.

Nobody is better placed to nurture cousinly relationships than grandparents. Children often find it easier to get to know each other on neutral ground. In their own homes, budding friendships can be blighted by over-competitive parents who compare their sporting prowess, academic achievements, even looks.

As cousins grow older, they grow apart, simply because they are bound to see less of each other. But they’ll always find it easy to pick up where they left off, their closeness underpinned by the shared experiences of childhood.

Rules of engagement

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