Does each member of a family need their own separate 50 GB of iCloud Storage at $0.99/mo.

If the organizer for family sharing subscribes to the 200Gb or 2TB plan, they can invite family members to share that one iCloud subscription. See - Share an iCloud storage plan with your family - Apple Support. Everybody still uses and accesses their data using their AppleID but you all can (collectively) use up to the limit of the 200Gb or 2TB of iCloud storage.

If you have Family Sharing each of you share the same 50 gb storage plan, or you can choose to upgrade the plan. See this: Share an iCloud storage plan with your family - Apple Support