Nostalrius Begins - Quality wow vanilla realm (1.12)

Theres a guy in burning steppes who plays one char and the second is following him, he says its his friends char he walks around the area and farms whatever he sees. I dont mind if its legal, but do something about it if its not.

read terms of use
understand terms of use
report it to a GM
if anything from the ToU is being violated

That could be considered multiboxing which is against the Terms of Use.

Take a screenshot, host it on an image sharing site like Imgur, and open an in-game ticket linking the screenshot and noting the names of both characters (Along with other info if possible like level, race, class, where you've seen him boxing, etc.) for GMs to investigate.