Call/Clock(Alarm) notifications from other phones

Hello everyone, a few years ago I setup my mother and dad’s iPhones using the same Apple & iCloud account of mine.. I did this to facilitate the download of apps, updates, sync/backup to the laptop and to list all phones/iPads in Find my iPhone.. strangely I have been getting lately random notifications - yet silent - on my iPhone such as a missed call notification from my mother’s phone or alarm notification at my dad’s phone, such notifications appear at the bottom right of my screen.. sometimes my parents find missed calls in their call logs while their phones didn’t ring.. it was an actual missed call on my iPhone and so on.. does anyone know how can I resolve such anomalies? i am not intending to create separate accounts for each as they do not know how to manage their phones on their own..