Is it possible to merge local data of two devices when one of them is not logged on?

How to merge data from another device which has been backed up to iCloud but now logged in with different Apple ID?

I have backup a secondary device to iCloud without manually transfer all its data to my primary device (same Apple ID). 

This second device is now logged in with different Apple ID. 

I now need to access its previous local data from primary device. Is it possible to merge local data of two devices when one of them is not logged on?