Despite bearing more than a passing resemblance to each other - spitting image or just enough to suggest that we're related, depending on who you ask - my younger sister and I have, among our close family and friends at least, always been defined by our differences.
Although there are just two years between us, when we were younger she was infinitely cuter; a podgy mass of white blonde hair and bright blue eyes, with a mischievous grin and a propensity for stealing chocolate. I was a gangling thing, with legs so skinny that my cycling shorts (ahem) were always baggy. I also had a tendency to break into song despite being utterly tone deaf. No, I can't imagine why our babysitters gravitated towards her, either.
Fast forward 10 or so years, taking into account a few arguments of epic proportions - borrowed clothes, copied hairstyles, spats over who got to be Baby Spice when we played Top of the Pops, that sort of monumental thing - and midway through our teenage years came the epiphany: we realised that we were far better off as allies rather than enemies. From then on we collaborated and colluded in an unheard of manner, congratulating ourselves on securing such coups as extended curfews and increased allowances.
Despite this new-found friendship, our differences remained: my little sister excelled at maths and science and has just qualified as a nurse, a career choice I admire wholeheartedly, but couldn't even begin to contemplate for myself. She is calm and considered, whereas I can be impulsive, and the girl is really very neat indeed - her teeny-tiny handwriting resembles computer-generated script, while mine can best be described as a scrawl.
She came to visit me in Dubai for the first time last week and as I stood in Arrivals impatiently waiting for her to appear on the horizon, I couldn't help but feel ever so slightly apprehensive.
What if things had changed; would that all-important dynamic that we've come to rely on still be in place?
I needn't have worried. She is as orderly as ever. At one point I found her tidying my saucepan cupboard (I know how to show my guests a good time) and when I stubbed my toe during an evening out, she was the only one in the group with a plaster in her handbag.
I, on the other hand, left piles of books on her bedside table, in an attempt to encourage her to read something other than celebrity magazines. At the end of the week, I had to cajole her into actually writing the two postcards she'd reluctantly bought several days earlier. In other words, all was as it should have been.