iCloud Family Storage - can you limit allocated space?

You can't specify how much space members of a family group can use. All members have access to the total space available. I'm afraid you need more iCloud+ space - or fewer members 😀

It sounds like it's time to step up to the next iCloud+ plan: iCloud+ plans and pricing - Apple Support

Apps would be a small contributor generally speaking but video consumes a lot of space. If you remove it from iCloud it may give you back a significant amount.

Don't make the mistake of moving it from iCloud without having it elsewhere on your devices or an external drive. iCloud syncs, it isn't a separate repository.

Apps and Film downloads do not count against the shared cloud storage.

The 2TB cloud storage is used by iCloud Photos, iCloud backups, iCloud Drive, and by apps syncing the data with iCloud, for example Notes, Calendar, Mail.

You will have to request from your your family group to be considerate and to remove the items from iCloud, that are taking up too much storage. Otherwise stop sharing the cloud storage and only share the purchases and other subscriptions. Then everyone will have to pay for the cloud storage they are using and be more frugal.

Thanks for that correction léonie. I had in mind the preservation of video in an iCloud Drive folder.