What determines friend code?

[BYOO]

Does anyone know what it is that determines the friend code on d/p/pt?

My brother and I both have an R4 with the same Platinum game downloaded from the internet and we want to battle against each other online. The only problem is, we both have the same friend code (so we can't battle). Does anyone know what it is that determines a friend code? Is there a way to change it with pokesav? Or would it work if we erased the data on one of the games and started a new adventure? Would we then get a new friend code like that or would we have the same friend code as before?

Thanks for the help.

(And yes, we do legally own the game Platinum for real)

[Illithian]

Starting a new game will indeed give you a new Friend Code, but I'm not sure what exactly determines your friend code. Its probably something to do with ID, SID, and your name, but someone with the facts will come at some point.

[Kaarosu]

A FC is tied to you by the game card and DS that you used to access the Wi-fi. If you connect to the Wi-fi with your game but using a different DS it'll assign you a new FC.

[Toffeuy]

So are the FC's randomly generated or is there something that will affect the FC?