Change Apple ID
My wife and I share an Apple ID on each of our phones. Can I change that so that we have separate accounts?
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. Then make sure full resolution photos are on the device. 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 set up Family Sharing to keep access to your apps. 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
