Somehow merged with another person's icloud?

Logged into the family Ipad for a few months, recently logged out so that my father could log in. He realized today, that all of my photos are on both the ipad and his phone, which they weren't previously shown on the Ipad when I was logged on. I received no option to keep or delete the data from the device after signing out. aside from this, my safari data--such as my bookmarks and reading list--still appear on the device.

Resetting the device would in theory fix this, but only for the ipad, as the photos deleted from there do not get removed from his phone. Is there anyway to remove these photos from both devices without having to manually delete them? These photos date back to 2016, as that is nearly 8 years of photos, you could see why I would be anxious to avoid spending the uncountable amount of hours it would take in deleting them. Not to mention, one of us would be the one deleting them, meaning either I'd have to see all of his photos, or for him, mine.