In fact I see this as a huge lack of feature in iCloud. Me and my wife have a 300+ Gb library with hundreds albums created. At this moment, I'm the only one with access to all our photos at the palm of my hand. She can only see the most recent photos she took on her phone (until we import them to the main library and loose them).
The only alternative Apple give us at this moment is to share every single album with her. This, beside the manual and boring work, does not solve our problem because it is not possible to even search shared albums by name, neither face recognition, search by places, etc. Family sharing at this moment is completely useless.
@Apple, please give us the possibility to more than one Apple ID (inside same family) contribute to the same library. You already have the technology, as if I configure another device in my ID it will sync with the library. I repeat: This is a huge lack in iCloud.