I see my husband's photos but we've NEVER shared an Apple ID!
Here's the deal: I used to backup my photos on an external hard drive, but a couple years ago, I switched to backing up with iCloud. When I did that, suddenly I could see my husband's photos but only from *before* that date. So all the photos on iCloud/Photos are my own since I started the backup, but his prior to that. All the faces that Photos recognizes as family members etc, are his (for example, Photos labels pictures of my husband as 'Me'). I know what you're thinking, but I swear WE HAVE NEVER SHARED AN APPLE ID. Ever. We each had our own accounts long before we met; my ID even uses my maiden name in my login. So, if we aren't sharing an ID, how could this be happening? To be clear, no other apps are confused; everything else in iCloud syncs appropriately with our respective accounts. Poltergeist or .... ?