Welcome to the 'two under two club', Kate and William!
The arrival of Princess Charlotte could spell major upheaval for the royal household, as any parent of two children under the age of two knows. But Heidi Scrimgeour, whose sons are 21 months apart in age, reckons George and his sister have the perfect age-gap
Parents whose children are less than two years apart in age share a deep understanding, and even a secret language. "Two under two?" a new acquaintance asked me when my sons were little. When I confirmed that my youngest son was born before my eldest's second birthday, my fellow mother-with-an-ill-considered-age-gap-between-her-kids drew close and whispered conspiratorially: "Me, too. Bloody bonkers, isn't it? But I bet they're the best of friends."
As Kate and William embark on the daunting task of bringing up two children less than two years apart in age, they too may momentarily question the wisdom of having two children in close succession.
Nothing can prepare you for the physical onslaught, let alone the mental demands of caring for two very small children at once, but I have found my friend's summation of the 'two under two club' to be spot on. My sons, like many of their peers who have a sibling close in age, are one another's greatest ally, closest confidante, and most faithful friend.
Which is why it angered me to read that the American Centers for Disease Control and Prevention recently issued an edict advising mothers to wait 18 months after giving birth before getting pregnant again, in order to avoid risking 'serious medical complications' for both mother and baby.
Clearly Kate paid no heed to such advice, and nor did I. The youngest royal, Charlotte, and her big brother are just shy of 21 months apart in age, exactly like my sons, now eight and 10.
I can't speak for the Duchess, but neither I nor my second baby suffered any complications during pregnancy or birth, and I am an ardent believer that having babies in such close succession - known broadly by the two under two club as 'getting them out of the way quickly' - holds enormous benefits for the whole family.
First, there are the practicalities of having children closer in age than those American experts advise. Your sleepless nights are relatively short-lived as opposed to spaced out over several years. One friend whose three children were born in quick successions says he and his wife didn't sleep past 5.30am for almost five years, but I think that's preferable to getting your sleeping back on track between kids, only to upend it again once you've remembered what you've been missing.
The same is true of nappies. For a year, I had two children in nappies, much to the horror of friends whose eldest children were fully potty trained before they bred again.
But I had the last laugh because I could whip both children off to the baby-changing facilities with ease, whilst my friends dragged newborns into tiny toilet cubicles so that older siblings could answer the call of nature, or pleaded with reluctant elder children to accompany them on nasty nappy-changing missions.
The clothes one child outgrows are also a ready-made wardrobe for the next in line to the throne. There's no packing away of clothes which emerge moth-eaten and out of fashion when needed again several years later. Then again, I doubt there's much call for hand-me-downs when you're an HRH.
Keeping two under two entertained is rarely a challenge, either. They like the same TV programmes, they can participate in the same activities, and family holidays aren't spent negotiating age-appropriate schedules around clashing interests.
But what really made me the envy of my friends outside the two under two club was nap time. While friends wept when the baby's nap time went awry due to school pick-up schedules or noisy older siblings, my boys slept after lunch every day at the same time, for two blissful hours. I bet Kate hopes that her children will share a love of many things together, especially nap time.
Of course, my sons also provoke each other to rage that no other human being invokes. In my experience, siblings who are two years or less apart in age often fight with an intensity that siblings with bigger age gaps do not.
So the playroom at Anmer Hall may become the site of many a right royal fallout in the years to come, but Kate and William can take comfort in the fact that the bonds forged between siblings who are close in age can also bend steel. One small caveat: I had always hoped to have three children, all close together in the age, but having two under two left me so discombobulated that I wasn't fit to contemplate procreating again for many years.
Which is how I came to follow my membership of the two under two club with a late entry into the 'crazy age gap' group. My boys now have a little sister, with a gap of seven and nine years between her and her brothers. Happily, this unlikely arrangement works wonderfully in terms of family dynamics, too.
So, if it's true that Kate and Wills kept the top three layers of their wedding cake in anticipation of the eventual patter of three tiny pairs of feet, I would advise leaving a few more years between the new princess and the arrival of the next royal baby. Indeed, the proud new parents might need that long to recover from having two under two.