Real estate is always at a premium, so why should online real estate -- namely cloud storage -- be any different? Some people have roommates to make ends meet, and some of us need a family member with a large iCloud plan to accommodate all those selfies. Fortunately, Apple offers shared iCloud storage, with a few notable restrictions.
Before getting started, your Apple iOS device (iPhone, iPad or, yes, even iPod Touch) needs to be running iOS 11 or better. This is only necessary for the primary device that's sharing its iCloud account, however, Apple suggests updating all devices on the shared account to the latest OS for the best experience.
MacOS devices (MacBook Pro/iMac/MacBook/Mac Mini) need to be running High Sierra 10.13 or better. Remember to always back up your devices before updating. If you need some help updating your OS, Apple has guides for iOS and MacOS.
Keep in mind that if a family member using more than 5GB of your storage space leaves the shared plan, they will have 28 days to purchase their own plan to secure their data, before reverting back to the default free 5GB plan.
While sharing a storage plan, documents and photos remain private, and everyone continues to use their own accounts within the shared iCloud storage. Family members are only sharing available cloud space, not personal data.