He is even-tempered and caring.
Benvolio's name comes from the Latin root "ben" which means good. In the opening scene of Romeo and Juliet he asks for everyone to put up their swords. He doesn't condone the violence. Also, when Lord and Lady Montague are worried about Romeo's isolating behavior, Benvolio talks to him to find out what ails him and comes up with a solution.
In my opinion, they do not only reveal what will happen, but also manipulate events. When Macbeth approached the witches, they could have concealed the truth from him and just let the events unfold, but they didn't do it. They told him about the prophecy, thus initiating the events that soon followed. If they hadn't told him the truth, Macbeth might have never killed Banquo, Duncan, and the rest in order to become king. So yes, they manipulated events and caused a great tragedy.