If they are not on the same IP then it is fair. Its just like if you are joining a game with a friend. However if they are on the same IP then that does count as cheating.
I don't see why this is such a big deal, they are brothers, they share an IP. SO WHAT? Just because they are brothers doesn't mean they are the same person. They are probably gonna back stab each other a couple of times when they join together.
You personally can't have 2 accounts. But if 2 siblings like Big Brother, why shouldn't they be able to be on tengaged? Just cos they help each other out means nothing, it's called an alliance. Shouldn't be punished for that. So yes, it's fair
7. Multiple accounts - (See definitions above regarding multis and red noses)
If you have a sibling on Tengaged or someone else who lives with you, PLEASE LET US KNOW ASAP. We will put a note on your account. If you don't let us know, you're subject to possible bans and red noses. In addition, duplicate accounts may be banned.