We continue explaining the operation of the Apple cloud and specifically the part that has to do with iCloud Drive, or what is the same, the part that has to do with space that we have free for file storage that we believe appropriate.
I already explained in previous articles that we should be careful with the files that are stored by both the macOS own applications and the data that the iOS applications save in iCloud Drive because that data is invisible to the user when we enter the iCloud Drive route either through iCloud Drive on macOS or in Files on iOS and even in iCloud Drive on iCloud.com itself.
Those files generated by the applications as well as they can only be generated from those applications, whatever they are, can only be deleted from them so you have to take that into account before uninstalling any application since otherwise that data will be left in limbo at a "higher level."
But let's go where we are going and that is that what I want to explain to you today is how to manage iCloud Drive storage when you click on "Manage family" within System Preferences> iCloud> Manage Family. The first thing you have to do if you want your iCloud Drive space to be shared with another component of your family is to configure the system with that new Apple ID of that family member, after which you will be asked what you want to give rights to that new person.
Among the options you can choose is to share your space in iCloud Drive and this is where what I want you to consider comes from. From here, you can only share your space with the rest of the people in your «family» group and you are not going to be able to give a certain person a few gigs as if you paid them a 50GB storage plan, for example.
If you want your child to have their own 50GB, you must have funds in their Apple ID so that from that ID you can select to have that storage plan. After doing that, each month that amount of space will be charged so either you are transferring gifts of money to that Apple ID through iTunes or you associate a credit card, which I don't think you want, or buy iTunes recharge cards to redeem codes.
In short, from "Manage family" you can only share your plan space. If you have 200GB of space, that space is shared for the accounts you designate without a cap for each of them. Of course, keep in mind that what is true is that your data will not be mixed with those of your relatives.