Okay, so I have a twin brother. If you don't believe me, I can make a video proving it. Anyways, I just found out that he made a VGChartz account (IranianAzeriUzbek). However, since we're only 15, we share the same house, and hence IP Adress. I am wondering about the complications that this will result in.

None.   User accounts are not based on IP addresses.  Otherwise, those with dynamic IPs would have serious problems everytime their ISP rotated their IP and those that used multiple computers on different networks would find their account unusable half the time.

What complications? Are you referring to illegal activities on the internet ? Not sure what you mean by complications..

I'm wondering if one of us will get banned because they'll think that it's an alternate ID, when in reality it isn't.

There are dozens of alt ID's already running around anyway so you'll be fine.

Nope.. I would assume whatever is done on one account only refers to that account.. Your brother is responsible for his account and you are responsible for yours. No complications at all

As long as you aren't BertleSenix or Yukara_Senix, it's fine.

(Seriously, you should be all right)

Shouldn't be a problem in general but if one of you will get banned for a post they will maybe also ban the other account but not sure about that.

Not likely.  They'd have to look up the IP in the database and chances are good that it would come up with multiple users simply because of the way ISPs rotate IP addresses.

I only know that i saw  mods saying from time to time "we made an ip check and it wasn't the same" when people thought someone has an alternate account. but that probably only happens if someone is a troll and a user of another account is acting exactly the same so yeah, you should be right.