If you are all using the same Apple ID then the location of that ID is being used by your son's iPhone. Only one iPhone can be used for location with an Apple ID. If you look in the Me tab in Find My you will see in My Location (iOS 16) the at the location is being shared from either "This iPhone" or on another iPhone it will display the name of the iPhone in command of the location.
Apple does not recommend different people using the same Apple ID. If you want to keep your locations separate you will need to create separate Apple IDs.
See
How to create a new Apple ID - Apple Support
Manage and use your Apple ID - Apple Support
Make sure that each family member has a unique Apple ID - Apple Support - in this document note specifically the advice:
Avoid sharing an Apple ID
Apple recommends that you do not share your Apple ID. Instead, set up Family Sharing so that each person uses their own Apple ID. This way, your family can share purchases, subscriptions, and more without sharing personal information like email, text messages, or passwords.