Backing up your iPhone or iPad is very important, as we tech journalists constantly tell our readers. You don't want to lose vital data or personally significant photos and messages. But backing up to the cloud can be difficult because of Apple's stingy allowances.
Each Apple ID gets a free 5GB allocation of iCloud storage, and that doesn't increase as you buy more devices; to operate a comprehensive backup programme you're forced to either pay to upgrade your storage or back up laboriously to iTunes (which carries its own risks).
But it's not all bad news. Since the launch of iOS 11, families have at least been able to share their iCloud storage, which means that one person can pay for extra storage and the rest can use it for backups. (This wasn't possible before, leading families to the absurd situation of paying for multiple iCloud subscriptions.)
Set up Family Sharing
iCloud storage sharing works as part of the larger Family Sharing feature, and you'll need to set that up first if you haven't done so.
You can set up Family Sharing on an iPhone or iPad (the easiest method) or on a Mac (which is slightly more of a hassle). On the iPad, you open Settings and tap your Apple ID at the top of the screen, then tap Set Up Family Sharing > Get Started; on Mac you open System Preferences and click iCloud > Sign In, enter your Apple ID and password and then click on Set Up Family.
In both cases you will then follow the onscreen instructions and invite members of your family, and they'll need to respond to their invitations.
We explain this process in far more detail in How to set up Family Sharing.
Enable iCloud storage sharing
Now that your family is set up, you just need to make sure iCloud knows that you specifically want to share storage.
Open Settings again, and tap your Apple ID/headshot at the top, then Family Sharing. (You may already be on this page having just finished setting up the family settings.) At the bottom of the screen you'll see Shared Features, which shows which of the four possible elements you're currently sharing: tap iCloud Storage to change it from Off to On.
If you're still on the free allocation, Apple will require you to upgrade to at least 200GB (which costs £2.49 a month) before allowing you to share: you're not allowed to share 5GB among four, which would have been a pointless idea anyway.
Tell your family
The last step is to tell each member of your family that you've set this up and tell them how much storage is available. If necessary you should walk them through the process of switching from manual or iTunes backups to automatic iCloud backups (Settings, tap your Apple ID, iCloud > iCloud Backup).
If space is going to be tight for this many people, you wish to upgrade your plan, or establish some rules about not backing up huge amounts of bulky video.
You don't need to worry about family members being able to see what the other members have backed up, incidentally. I suppose this cuts both ways: another way of putting it would be that your kids can back up whatever they like without you being able to check it.