Do Damon and Stefan know ??

yes they do.. at least damon does because he found out by caroline, who has been helping tyler through the whole process.

I think so because didn't Caroline tell Stefan about it in a Назад episode?

Yes they both know because in 2x08 Caroline tells Damon how Tyler killed Sarah and how his eyes changed color also in 2x11 Damon tells Elena and Jeremy that Caroline's on werewolf duty and in 2x09 she tells Stefan how Tyler's freaking out because a full moons coming up.

Yes they do know.

YES THEY DO ! CAROLINE WAS THE ONE WHO TOLD DAMON , AND DAMON TOLD CAROLINE THAT SHE CANT BE HIS FRIEND !

yes they do. Damon and stefan both know