Where are you seeing the the photos on your son's iPhone?
Are they in the Shared Family album?
Or did you enable the Shared iCloud Photos Library? If you have set up the Shared iCloud Photos Library on your own iPhone, you may want to remove the photos you do not want to be visible on the devices of other family members from the Shared Library back to your personal library. And disable the sharing of photos right from the camera, or each and every photo you take will automatically appear on all devices of the family members.
See: How to use iCloud Shared Photo Library - Apple SupportApple SupportOfficial Apple Support › en-gb