Does sharing a iCloud share Photos library duplicate the Photos library size?

Greetings MRYFLYGUY,

According to the resource you used to reach us:

"When you contribute photos and videos to iCloud Shared Photo Library, they move out of your Personal Library and into the Shared Library. You can join one Shared Library, and you can choose what to share, or automatically share content straight from the camera. All participants have equal permissions to add, edit, and delete content in the Shared Library, while the person who set up the Shared Library, the library creator, provides iCloud storage for all of the content. Everyone else gets access to the Shared Library content without it counting towards their iCloud storage. 

When you join a Shared Library, iCloud captures a one-time snapshot of your photo library database and associated metadata and stores it for up to six months. This helps with a smooth transition of your content to Shared Photo Library. Any photos that were in your library at the time of the snapshot that are subsequently deleted are also stored in iCloud for up to six months. " How to use iCloud Shared Photo Library

We hope this helps!

Sincerely.

Hey MRYFLYGUY,

Welcome to Apple Support Communities.

The same location(iCloud) is used however the library is called iCloud Shared Photo Library.

If you need to remove photos form an iCloud Shared Photo Library back to your Personal library on a Mac, check out the steps here: Remove photos from an iCloud Shared Photo Library in Photos on Mac.

Take care.