Invalid Alt Account missunderstanding.

So i was gonna go to TF2 outpost a normal day and i was banned from there?
So I checked why i was banned from the link on steamrep and im banned for having a ALT - Account?
That's not mine , that's my brothers account and becouse i am his older brother he copies alot that i do and thats why he has a profile picture from the same game that i have.
This is not my account and i can tell my brother to log in to it sometime while im in aswell so you can see that it's not my alt.
Any more questions?
I don't know how you spot Alt Accounts but i guess its from the IP and we are on the same net..?
Or is IP from the same net? IDK but i believe its a misunderstanding and now i got all the tags that he got "Rawr scammer SR scammer" i just want to be able to use tf2 outpost again please?
Thx
-Gobbler