Increase family member’s iCloud storage
I have the 2TB iCloud storage that I have shared with the family. How do I increase a family member’s share on iCloud?
When you share an iCloud storage plan, all family members have access to all unused storage on the plan. You cannot allocate or limit the storage available to them.
To share, you need to use the instructions in the "Share iCloud+ with everyone in your family" section of Share iCloud+ with your family - Apple Support and if they currently have their own paid plan, they need to use the instructions in the "Switch from your iCloud+ plan to your family plan" section.