ello Dazoti,
Thanks for using the Apple Support Communities. We understand that you're experiencing an issue with some of your data showing up on another iPhone that is not yours. When you updated your iPhones, did you happen to do it through a computer or has your sons iPhone recently been restored?
If you haven't done so yet, you might want to go through all your device settings and your sons to see if there is a location your contact details are showing on each other’s device. The best place to start is by looking at your Messages and FaceTime to see if both Apple ID's are listed or your phone numbers listed on each other’s devices.
iOS devices:
Settings > Messages > Send & Receive
Settings > FaceTime > You can be reached by FaceTime at
Mac:
Messages app > Messages > Preferences > You can be reached for messages at
FaceTime app > FaceTime > Preferences > Settings
To help guide you:
Add or remove your phone number in Messages or FaceTime
Set up Messages on Mac
Set up your iPhone and FaceTime on Mac for phone calls
If you find that any of your details have been cross mingled, simply remove the unwanted contact details from the feature.
Best regards.