False complaint and FIR registered

Due to property issue where was a physical fight between myself and my 2 cousins, who caused bruises on my right shoulder, punch on my forehead and tore my T-Shirt. My wife who was carrying my younger daughter was pushed. My Aunt who has not been keeping well was actually tying to pull her sons from the fight got injured. Her wrist got fractured. Since I complaint first to the police who considered it as a Non Cognizable offense, my cousins reported another complaint against me and my wife saying we hit her and that caused the fracture. This was considered as a Cognizable office and a FIR was registered against me and my wife. In her complaint she mentioned lot of things which are not true. My question is just because someone got damaged more than the other, how does the law works? The fight was triggered by my cousins, I was hit and my wife pushed and my Aunt got injured when trying to stop the fight and neither me nor my wife try to hurt her gets the advantage. As the FIR is already registered, it will be processed via court. Can a defamation case be registered against them? thanks in Advance