It's the ultimate sod's law of parenting: a close friend has kids roughly the same age as yours, so you eagerly anticipate hanging out together en famille. Your children will surely entertain one another for hours on end while you and your friend to put the world to rights. Perfect.
Except your child hates your friend's child's guts, and even a matter of minutes in each other's company is guaranteed to end in tears.
It's almost as though our kids do it on purpose just to thwart our best efforts to eke out a bit of fun in between all the drudgery that seems to go along with motherhood.
I jest of course. It's not all drudgery and I'm sure our little darlings don't really pick their enemies (or their friends) just to spite us. But if you've ever suffered the dawning realisation that your social life is about to be seriously curtailed by your child's inability to stand the sight of your friend's offspring, you'll know how awkward the situation can be.
It shouldn't come as a shock - it's hardly rational to assume that our children will like our friends' kids just because we happen to like their parents - but then we often overlook the fact that our children aren't extensions of ourselves.
This happened to me when my first child was born. A neighbour in the building where I lived had become a mum at around the same time as me, and we were giddy with delight at the prospect of hanging out together during the last few months of our maternity leave.
But it was not to be.
For reasons I've never been able to fathom, our tots just didn't hit it off. It's not that they fought or clashed - that actually might have been easier to deal with than the slow-burn of irritation and simmering resentment that seemed to exist between our warring children - it's just that spending time together always seemed to end with both our kids in meltdown mode.
It didn't seem to happen with any of our other friends, and I can't say it was anything the other child did. Our children just simply didn't get along, and eventually we politely stopped making plans to get together.
I felt genuinely sad, and even mourned the loss of a friendship that I'd had high hopes for. First time motherhood can be an isolating and discombobulating experience at the best of times; throw a strained relationship and a dose of disappointment into the mix and you've got the recipe for a full-blown pity party.
Looking back, I wonder if the friendship might have been saved if we'd found a way to talk about the issue. My friend Tamsin recently discovered that tackling a clash of toddler personalities head-on can help to ease the strain it causes.
"The son of one of my closest friends just irritates my child no end," Tamsin explains. "But instead of getting all precious or offended about it, my friend just shrugs it off and says 'They're kids. They'll get over it.'
"She's right, and that approach has rubbed off on me. The children's clashes invariably blow over so we've agreed that it's just not worth letting them destroy our friendship or curtail the time we spend together."
But not everyone shares such a pragmatic approach. My friend Beth vividly remembers being made to socialise with her mother's best friend's daughter, with disastrous consequences.
"I got on well with this other girl when we were little, but when we started getting pubescent I suddenly decided she was a crashing bore, and appropriately enough she thought I was weird," Beth explains.
"But my parents insisted that I invite her to my birthday parties so my school friends and I concocted a plan to be really horrible to her at my sleepover. It was proper mean girls nonsense, to my shame, but we made the mistake of writing down our plans for how to leave her out.
"My parents found the notebook and had never been more angry or disappointed with me. My birthday sleepover was cancelled - but my mum admitted later that she knew she'd made a mistake in forcing us to be friends even though I'd been complaining about it for some time.
"She ended up having to have a delicate discussion about it with her friend, which ultimately led to them growing apart, since having daughters the same age had been the main reason for them meeting up. Meanwhile I learned never to write down my bitchiest thoughts."
It's a cautionary tale, but I can't shake the conviction that no childish personality clash should ever be allowed to derail an adult friendship.
Indeed, my friend and I could have concluded that our meet-ups might be best arranged without our kids in tow, but it was company in the trenches of stay-at-home motherhood that we both craved.
And yet I'm also of the view that letting stressful play dates slide is a small price to pay for safeguarding your child's emotional wellbeing. Repeatedly exposing a child to a relational encounter that challenges them to the core isn't fair, and to do so in the name of friendship seems like a woeful mix-up of priorities.
Maybe teaching a child to suck up their differences and be nice for the sake of the grown-ups would go some way to teaching kids essential life-skills like resilience, but it seems just as likely that it would case resentment.
I want my children to understand that it's never appropriate for them to dictate our family social life on a whimsy - I'll always expect them to make an effort even with children they don't get on with - but neither do I want them to grow up believing that mum always puts her pals first.
So until I've cracked this particular conundrum, I'm going to cling all the tighter to those precious friendships that both the kids and I enjoy. They're worth their weight in gold.
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