You can share iCloud storage space with your family - and many other things - by creating a Family Sharing group.
See what Apple says about a Family Sharing group at What is Family Sharing?
Then Set up Family Sharing
"Family Sharing makes it easy for up to six family members to share music, films, TV programmes, apps, books, subscriptions including iCloud+ and more, all without sharing an Apple ID."
When your members are joining the group they can accept the offer to share your iCloud storage plan. At that point they migrate to your iCloud storage plan.