Spin Bros is more like the opposite of Jump Bros. The attack starts with Luigi moving behind Mario. Luigi then jumps on top of Mario. Pressing B when Luigi is above Mario will cause him to land on Mario's head and jump above him, spinning in the process. The Player must press the A button to make Mario jump on top of the spinning Luigi. The player has to press A again to fly over above the enemy. Now the player must press B to cause Luigi to let go of Mario and fall down to the enemy. When Luigi land son the enemy, B must be pressed to do damage.
There is another version of Spin Bros, when the Wario Bros are piggybacking on the Mario Bros. It starts the same, with the press of B to launch Luigi/Waluigi inot the air and start spinning. A must be pressed to jump up, but X must be pressed afterwards to land on Luigi/Waluigi. A is pressed to fly over to the enemy, B is pressed to let go, but Y is pressed apon landing to do damage.