How to Merge my Family to one iCloud without losing there info

My wife and 3 kids all have iPhones and iPad hat are backup to their own 5GB clouds and they are all full. I upgraded my iCloud capacity to 2TB and now i want to merge everyone onto one i cloud but i want them to be stored in the separate areas i.e. child 1 iPhone, Child 1 IPad, Child 2 Etc Etc. How do i make that happen without changing their profiles or letting them know I backing it up to my parental cloud?

Hopefully this question is clear, i am not a fluid mac person (obvious statement if I am posting lol).