Considering it's you and your brother, Gun Mayhem 2 is a fun game. If you're looking for something singleplayer, go for Strike Force Heroes series, Raze series and Armor Mayhem.
If you want a rail shooter, Sierra 7 is the best.
Hello. Bullet Heaven 2 is great for co-op (up to 4 players). First player on mouse and second on keyboard. Well, it's not a shooter strictly speaking, it's bullet heaven but a really good and challenging one.
