I can’t Setting up for a Family Member requires a GPS + Cellular Apple Watch Series 4 or later that is running watchOS 7.0 or later.
what I can do?
Hello, DRKVIMON, thanks for reaching out in reference to your Apple Watch. To make sure we're on the same page, can you tell us more about what you you're looking to do? Do you need to add another line of service to your account for the watch?
-Lauren