report him?

I hope you reported him? There should now be a "Report User" button on his profile.

But not to have more than one SG account. Even if you have someone (a brother, sister, whatever) accessing the website from the same location, you have to send message to admin and provide proof that those two accounts are valid and used by different people, and not just you.

A friend of mine is banned here, because his friend logged in on his PC and he did not give support a heads-up. They definitely check the IP and banned both instantly. :D

+1 i have a bro

You should try reading the rules before you ask more questions that are already answered in them.

That is very bad idea, NAT is common thing and thus forces to share ip, or you might get unlucky and hit IP someone has used earlier...