Family Sharing on ICloud account

See this support article:--> Share iCloud+ with your family - Apple Support

Regards

Giulio

You cannot add someone to your iCloud account. If you have setup Family Sharing, they can share space in your iCloud Account if you have the right size account. To share space in iCloud requires at least the 200GB size tier. From there you can share space when you are in Family Sharing.

Sorry, I was incorrect, the 50GB plan works, but check the link that Giulio provided for additional information.