Find My using email not phone number

We're starting to use Find My for the family, I can see my wife and my niece and they can see each other.

But when I told Find My to share my location all the time it seems to have shared my email, not my phone number.

When I look at them in Find My I see their icon and a name and a town.

When they look at me they see my email address and town - they don't see my name.

My niece sees a location for my wife, but not for me.