how to remove apple id from a paired phone to use as seperate phones

"Use these steps to remove your personal information from a device." Click here --> What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

then

Set up your iPhone, iPad, or iPod touch - Apple Support

and How to create a new Apple ID - Apple Support

Or if you want to keep the data, when changing to the new ID, make sure you turn off Find My Phone before signing out of the old ID. Once signed out and Find My Phone is off, then sign in with the new ID, then turn Find My Phone back on. 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. See Winston Churchill's response in the below discussion. If possible, also set up Family Sharing  between the IDs to keep access to your apps/purchases. 

 How to switch Apple IDs on your iPhone or iPad.      

 What to do after you change your Apple ID or password - Apple Support.    

How to transfer all files from one iCloud account to another.    

Family Sharing.         

Family Sharing - Set up.