Each family member will have their own separate Amazon account under your main Amazon Prime Account.
As mentioned before, shipping cost is often a deal breaker, so Amazon has sneakily waited until this final checkout page to show me how much shipping will cost.
Everyone in my family uses my brother's account when we need to use Prime.
The content management for the child profiles is much more granular and you have to explicitly approve each title in your media library for access.
It is definitely better organized.
After setup, you will still be able to manage or change your shared content.