First of all- how old are you and your brother?
(im not trying to be creepy in any way- im just trying to help. Rememer to not give out any personal information.)
And second- i know most people say getting back at them, or using mean words is the wrong thing to do... but in cases like that, you kinda have to. I dont know you, but similar accusations have been said about me. And i promise you. they forget. It might be terrible for a while...but just remember that they are kids and they are gonna say messed up things.
Just do something permenout to a temporary problem.
(im 15 by the way)