iCloud storage
f you share iCloud storage wit someone is the storage kept separate per user
Question marked as
Are you are using iCloud Family sharing, as described here? Use iCloud with your family - Apple Support
If so, then the answer is yes. All of the data is private to each user, as described in this Apple Support document: What is Family Sharing? - Apple Support
Everyone's personal files and preferences stay private
When you share iCloud+, family members can't see each others’ photos, files, or documents. And when you share other subscriptions like Apple Music, Apple Fitness+, or Apple TV+, each person sees their own preferences and recommendations — not the whole family’s.