Sometimes you sort of know you might have made a rod for your own back, right? You hope it's a bamboo sort of rod, a flexible one you can bend a little at will – then you realise it's actually solid oak and you're going to have to take an axe to it.
The rod I'm talking about is the fact that, for such a long time, Ava and Ruby have been treated perfectly equally. With only a year's difference in age, ever since Ru could move, there has been so little between them.
Ruby certainly does not recognise any difference between herself and her big sister. They attend the same nursery on the same days, they share friends, they share clothes, they enjoy the same activities and clubs. They go to bed at the same time. They are always together.
Well, a bloody great cavernous gap is about to open up between them, as was highlighted to me last week, when a package arrived for Ava with the post one morning.
Two black skirts, four white polo shirts and five pairs of knee-high white socks – her new school uniform – were excitedly unwrapped and waved about. Naturally, she wanted to try it on straight away. Despite the fact I was trying to coax both her and Ruby (who'd run off into the garden) into leggings and T-shirts for nursery, and despite the fact I was quite keen that all items of uniform remained clean at least until her first day, I figured we'd better see sooner rather than later whether it all fit.
She picked the skirt she liked the look of best, and pulled it on with glee. A polo shirt was grappled with and, before long, attached to her the right way round. Socks were stretched to their limit until they were thigh-height.
The overall look was slightly on the baggy side, but Ava looked as proud as punch. And, probably, so did I.
Ruby returned from her garden adventure... and promptly dropped her bucket of snails on the living room floor when she saw her big sister.
"Ooooh," she said, gently stroking Ava's top buttons.
"It's Ava's new school uniform," I said. "Remember Ru? Remember I told you that Ava is going to start going to school soo...?"
"I like school uniform, too!" Ru interjected grinning.
I began explaining again that Ava was going to school and Ruby wasn't going to school, but the words were lost on her. She had seen the other skirt, and the other tops, and was claiming them already.
"Ru, these won't even fit you. And you don't need school uniform, darling, you're..."
"It FITS, Mummy!" Ruby squealed as she desperately squeezed her head through a top without undoing the buttons first. Arms in, the garment hung almost to her knees.
"It's a bit big, honey. But NEXT year..."
She was already putting the skirt on. She pulled it up around her tummy, then let go. It promptly dropped to her ankles.
"Next year, you'll have your own school uniform!"
"Noooo!" Ru cackled. "THIS my one. THAT Ava's one. See? Fits!"
She pulled the skirt up again. Again it slipped off. She whipped it up and held it there, hoping I hadn't noticed.
Ava ran off to show Dan her new look (she is SO not going to be excited about it when she realises she has to wear it every day). Ruby did a little twirl, her hand grasping the back of the too-big skirt.
"Darling," I said, "This school uniform is Ava's because she is going to start school soon. And you are going to keep going to nursery, with all your lovely friends, for one more year."
Ruby looked at her feet. "I go to school, too," she said quietly.
"I'm afraid you can't, not just yet. But you love your nursery, don't you?"
She nodded. But her bottom lipped popped out.
"So, shall we put Ava's uniform away, and get you dressed and ready?" She let go of the skirt and it dropped to the floor.
I have no option but to prepare Ruby for what she in no doubt going to consider the unfairness of it all – a whole year when Ava gets to do all sorts of things that Ruby doesn't. When Ava came back and also removed her uniform, Ru cheered up immensely, and for a while it was forgotten...
Until, the following day. In the kitchen, I said to Ava (thinking I was out of Ruby's earshot): "We'll have to go and get your school shoes at the weekend!"
Little feet thundered down the hall, a little face appeared at my side: "I like new school shoes, mummy!"
You can read Pip's previous columns here.