Hi there,
The better progress is that the family member comes to us to ask for deleting the registration.
But if you are able to provide the name and the accurate email account that the family member registered the product with, and a picture of the invoice, we can also help to adjust.
To be honest, the registration only affects the warranty, which is also based on the invoice. So if the invoice is the same, there is not much difference to change the registration.
Thank you.