I don't think so. Multiple accounts per IP is allowed here. Just make sure you don't do something stupid probably like spamming referral links or spamming unnecessary stuff; as you can probably both get banned by doing so, as both of your accounts are registered and being logged in on one single IP address.
me and my brother joined bitcointalk, lul
![Cheesy](https://bitcointalk.org/Smileys/default/cheesy.gif)