Years ago, before I had kids of my own, I'd occasionally be entrusted with the care of my niece. My sister-in-law would invariably return home to find me and Rhiannon, her daughter, hopped up on butter icing, having failed to eat anything even vaguely containing a nutrient, and the kitchen approximating a Jackson Pollock reject owing to a mishap with the electric whisk. "But look!" I'd say, "we made edible dominoes. Her counting's brilliant!"

I loved those afternoons. It was great to get to know my niece, who was even then very much her own person. We were building our own relationship, separate from the rest of the family; and even though it was largely butter-icing-based in those days, it was something I very much valued. There aren't many relationships in life, outside of those with your children, where you get to know somebody from their beginning.

Shortly after the edible-dominoes incident, presumably to the huge relief of my sister-in-law, my husband and I left the country. For the next seven years, my interactions with Rhiannon were briefer, and limited to family gatherings on trips home. By the time we returned permanently to the UK, we had two small boys of our own, my auntdom included another niece and a nephew, and the five year old who had relished electric-whisk lollipops was now an astonishing 13. There were swaths of Rhiannon's life that I just hadn't been around for; huge tracts of her personality that were entirely unknown. So, when I found myself making weekly work trips to Rhiannon's home town, it felt right to take her for dinner and get to know her again; to rekindle that bond that should, by right, last us both a lifetime.

Thirteen is a wonderfully bonkers age. Neither child nor quite yet adolescent, Rhiannon is, as my four-year-old put it, "a grown up for children". Because best friends are vital to a 13-year-old girl, Rhiannon's BFF comes with us for dinner. Both are great company; polite and engaging. Conversation veers wildly, one minute covering the three "B"s of school life (boyfriends, Blackberries, bullying); the next earnestly discussing whether rocky road is a better sundae topping than chocolate brownie sauce.

I'm aware that I'm getting the best of all worlds. It's easy to be the auntie who swoops in to let someone pick where to go for dinner (the only rule: after two consecutive visits, we have to try somewhere new because 13 is too young to stagnate) or to go shopping for a new outfit for the birthday disco. It's very different from fraught discussions about homework or bedtime. But, to an extent, that's the fun of it, hopefully for both of us. In a world of homogeneity, it's just nice to spend time with someone from a different generation, someone I know I have decades with which to build relationships and memories.

I was – am – lucky to have a large extended family. As a small child, I didn't ever stop to think about this; it was simply my universe, a universe in which there was always an auntie to make doll's clothes, an uncle to proffer toy racing cars, a bevy of relatives to scoop up a job lot of cousins and take us all to the seaside.

The advantage of an aunt (or uncle) really kicks in from adolescence. Your parents' siblings are, with luck, the bonus ball in the lottery that is extended family; the perfect blend of family and friend. Parents, however great, can't be impartial observers, whereas a well-placed relative will know your family history almost as well as you but is one step removed.

The summer I was 18, I failed my driving test for the third time. Passing my test was the ultimate in independence for a country kid like me; at this point I'd spent enough on driving instructors to keep them all in dual-steering and sedatives for life, and my parents had wisely opted out of the role on the grounds that we all needed to get along – and to stay alive. So an uncle, Morris, was drafted in.

Morris had nerves of steel, preternatural patience and such a devotion to Chris Rea's Driving Home for Christmas that he'd made a 90-minute "mixtape" consisting solely of this one song. That it was July made no difference whatsoever– seasonal variation was for wimps. Together, the three of us – Morris, Chris and I – logged hundreds of miles, meandering in endless loops around the narrow lanes of the Forest of Dean, following the oxbow lakes of the Wye Valley as the sun set over the oaks and sent the light dappling on to the road surface. Morris succeeded where all others had failed, imbuing me with enough confidence to pass my driving test and passing on a skill for life.

The other, less obvious legacies of that summer have aided me throughout adulthood. I learned to relate to an adult who wasn't my parent or a teacher –a hugely valuable skill when entering the unfathomable world of grownups. I saw my parents refracted through the eyes of their peer, a view I'd never before been party to. And I developed a Proustian connection to Chris Rea so enduring that the opening bars of his "masterpiece" instantly evoke the tang of summer air heavy with ripening fruit as I steered erratically past the fields.

Even once you're past the age of actively needing adult supervision, the sense of rootedness that can only really be evoked by a relative is still inestimable. I went to university hundreds of miles from home, but just up the road from my mother's sister, June. In the midst of the euphoria and chaos of freshers' life, it was enormously stabilising to escape for dinner with a family who'd known me all my life, who didn't care which subject I was studying. It could be poignant, too. Walking home after a lecture early on, I caught sight of June popping in to visit. Her twilit silhouette so exactly resembled my mum's that the lump of homesickness rose to my throat unbidden.

Having a nearby aunt was covetable. June soon found herself taking a group of us for coffee, everyone wanting "aunt time"; and when I lived abroad in my third year, she became honorary auntie to my friend Theo, tending to his houseplants in the holidays.

Spending regular time with Rhiannon, something that sprang from a nebulous sense of it being an aunt-like thing to do, has had huge, beneficial ripple effects. On a very superficial level, it gives me a glimpse into what parenting a girl might have been like. The mother of two small boys, I doubt extensive discussions of nail polish technique and trips to outlet malls are otherwise in my future. But far more than that, it's given me a deeper appreciation of my wider family.

Now I'm at the other end of the relationship, the aunt rather than the niece, I'm grateful anew to my many aunts and uncles for the generosity of their friendship over the decades. I've gained even more respect for my endlessly tolerant sister-in-law; and my sons, now seeing this as the norm, ask to spend time with their aunties, going off proudly to have lunch with my sister and her daughter. It's the biggest cliche of all, but kids grow up so fast – and when they do, they turn into adults. As a parent, if for any reason my children felt they couldn't talk to me about something, I'd feel hugely reassured knowing that they had strong bonds with their aunties, a home-grown safety net.