Why don't you ask him to connect to the server and create himself an account? I don't think you can create another account whilst you've already linked one.
If he can't create an account for himself, You can create one for him. But, DON'T use his account because you will be punished.
He can not create a new account on the same PC.I managed to create new one, as my current one is made in 2016 when I had another PC. So now he have an account made from my current PC.
Yikes, im asking something else. Is that allowed?