my brothers pictures are in my photos and mine are in my brothers photos
Are you both using the same Apple ID for iCloud? If so and if you have iCloud Photo Library turned on, the photos will sync. See: iCloud Photo Library - Apple Support
Are you both using the same Apple ID for iCloud? If so and if you have iCloud Photo Library turned on, the photos will sync. See: iCloud Photo Library - Apple Support
To avoid this, one of you needs to create a new Apple ID. Ask you parents if they will set up Family Sharing to allow you to share purchases.
There may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. Also see Winston Churchill's response in the below discussion
How to transfer all files from one iCloud account to another
Apple ID email address or password - What to do after you change
Family Sharing - Use your own Apple ID for Family Sharing
Family Sharing -What types of content can I share?
Family Sharing - If you don‘t see your family‘s shared content
Family Sharing - purchases and payments
Family Sharing - Hide and unhide music, movies, TV shows, audiobooks, and books
Family Sharing – share iCloud Storage
Family Sharing - Share an iCloud storage plan with your family
Family Sharing and Apple ID for your child
Why do I have all my brothers pictures on my phone
