The UK has been in a fever of nervous anticipation for the past few weeks, with the nation's attention focused on an event featuring red-faced shouting, sleeplessness, calls for "one last push" and cries of "I just can't do this any more". But away from the general election, there was a rather more pleasant story: the birth of the copiously named Charlotte Elizabeth Diana Windsor, Britain's newest princess.

Amid the consensus response of "Doesn't she look cute – where can I get one of those bonnets?'' we should spare a thought for His Royal Displacedness Prince George, on whom, right about now, it will be slowly dawning that the noisy bundle his beloved parents brought home from hospital isn't going back.

There's nothing quite like the bittersweet weeks you spend with your PFB (Precious First Born, as Mumsnet users have knowingly termed them) when you're heavily pregnant with your second –especially if your oldest is too small to really comprehend the baby-shaped train that's coming down the tracks.

For their entire short lives, the PFB has been the unchallenged prince or princess of its parents' hearts, monarch of all it surveys. The shock (and, in some cases, fury) caused by the arrival of the new interloper can take months, or even years, to alleviate. Some older siblings – well into middle age – will confess that it never really abates.

What to do? Some Mumsnet users talk of simply choosing to stop at one child; the luscious cocoon of parents (or parent) and supremely loved child, for them, is just too precious to disrupt and all the parental resources and attention can be lavishly focused on just the one. Most parents, though, like the Cambridges, press on for a second (no doubt in the hope that it will release them from the role of chief Lego playmate).

Give them responsibility - and toys

Mumsnet users have many tried and trusted strategies. The Duke and Duchess could try having a basket of new toys (charity shop or otherwise) to produce one by one for George during those long periods of feeding in the early weeks. Other tips are to give your PFB some "jobs" – chief producer of clean nappies, grand high poohbah of the flannel – to give them a sense of glorious competence and responsibility. Moments of eye-rolling collusion between parent and child when the baby does something ridiculous or smelly can go down a treat.

In general, the word is to try to prioritise your older one when it's possible and practical to do so: Charlotte may have to be left in her bouncy chair a wee bit longer than George was. As a Mumsnet user writes, wisely: "'The older child does need to learn that the baby is also a person who has rights and needs, but not necessarily immediately."

A baby yawns inside the maternity ward of a hospital in Taipei

Given the propensity of otherwise lovely fathers-to-be to behave like eejits, it's a wonder second children are ever born. As one Mumsnetter wearily remarked: "Next time I think I'm just going to velcro him to the wall.

Read Justine's guide to the dumb things men do during their wife's labour here.

Expect and allow for some bitter feelings, confusion and acting out from your older child. Above all, the trick is to acknowledge the older child's feelings, even if they're not always very nice. It's not unreasonable or awful for them to feel upset or angry, and it's OK for these things to be spoken out loud.

One Mumsnet user tells of her older child drowning the baby's dolls in the loo: you don't need a qualification in psychoanalysis to work that one out, but so long as fratricidal impulses are being played out through inanimate proxies, the trick is not to worry overmuch.

A recent discussion focused around our users' own confessions of ways in which they'd treated their siblings as they were growing up, culminating in a magnificent tale of "taking all her stuffed animals, putting them in giant ziplock bags, filling them with water and putting them in the freezer". We're sure everyone involved is completely fine and over it. Probably. And if not, we've heard regular therapy sessions can be awfully cathartic.

As with so many things in parenting, it's a question of hanging on through the tough bits and reminding yourself that it won't always be this way. In about five years' time both children will (hopefully) be merrily conspiring against you, and won't be able to imagine life without each other.

Having two little ones so close together is hard at times, undeniably; but as one user put it: "Seeing my son stroke my daughter's head or hold her hand makes all the difficult stuff just melt away." Until then, CBeebies is your friend, and Will and Kate need just remember the parental mantra: No Guilt. And to be thankful it's not twins.

Justine Roberts is founder and chief executive of Mumsnet and Gransnet. She has also sat on the Expert Steering Group on Family Support Services, the Consultative Council of the British Board of Film Classification and the Commission on Civil Society and Democratic Engagement.

You can find her own Twitter @Justine_Roberts, or visit the Mumsnet page @MumsnetTowers. Alternatively, for all information about Mumsnet please visit the website here.

On 16 May Mumsnet is holding its annual Workfest event in London, featuring talks from the likes of Jo Swinson MP, Shami Chakrabarti and Anabel Karmel MBE. For more information please visit the website here.