Can I migrate a family member's icloud storage to a family sharing plan without losing their data?

When you share an iCloud storage plan, the family members' storage stays where it is and continues to be accessed by them using their Apple ID. There is no migration. The only change is the amount of storage available and the billing. Share iCloud+ with your family - Apple Support

Each person has access to any free space in the storage plan. There is no option for you to manage each person's space.

If you do the following, is your wife listed there?

On your iPhone, iPad, or iPod touch

1. Go to Settings > [your name].
2. Tap Family Sharing.
3. Tap iCloud Storage.

Got the big family plan and invited family members to join. My wife's phone continues with no space, and photos don't go to iCloud. is there a limit of space each family member has available? where can I manage each persons space?