You turn on/off iCloud Photos...you don't sign up for it. (You sign up for iCloud+ if you're needing more than the standard 5GB storage space.)
If you're wanting to share the same photos, you can set up a Shared Album. It does not use your iCloud storage space, but you'll be limited to 5,000 photos/videos though. This does not require signing up for an iCloud+ subscription.
Share photos and videos easily with Shared Albums.
support.apple.com
If you meant signing up for iCloud+, then yes, you can share the storage between the two of you with Family Sharing. Note: This is sharing storage space...not photos. You each would have your own private photo library.
iCloud Shared Photo Library lets you share photos and videos seamlessly with up to five other people, so everyone can collaborate on the collection and enjoy more complete memories. Learn how to set up and use a Shared Library.
support.apple.com
This article explains the differences between Shared Albums and iCloud Shared Photo Library.