Q: Facetime call list shared

I share an Apple Id with my 3 kids and in every iphone, ipad or iPod I registrated their own number of email adres at message and facetime so we all get our own calls and messages. But only the ipad mini of my son and mine iphone 6 keep on sharing callers information on facetime  Ik see the calls he made with it and he could see what I did. I chec ked everything.