as for his brother he only appeared in the pilot ? so i guess he just got wrote out of the series as imo the brother was a pointless idea anyway and with the exception of him joining up with sam (too much like supernatural)
He appeared in episode #2: Charged. Sam got a Prius, which he complained about. Then when the Prius got wrecked by the soul be complained even more, saying he would never let anything happen to such a gift.
Beyond that, he was mentioned later that I recall. When Sam tells his mother about being a Reaper at the end of the episode she states that they shouldn't keep any more secrets... except from his brother (which Sam immediately agrees with).
It's possible the brother is gone for good story-wise or because the actor got another deal. In any case, I wouldn't be surprised if he was gone for good OR if we saw him in some random episode.