dmansland is right.
Well here is a tip or something like that. When you start fighting the second form, it's IMPORTANT that at least one of the Bros survives. Well if one dies, use a Max 1-up Shroom, or if both are alive, like dmansland said, use a Max Nut. The begining is shitty because if you get hit one time=death.
By the way Puddin, planning to start playing Partners in Time later?