How can i reset positions of Prefab children's in unity 2d. children's are also prefabs

I have an object which is prefabs and that object contains further objects(assets) which are also prefabs. I want to Reset position of Parent object and Children object when level fails. however I am not able to reset position of children object by instantiating. I can instantiate parent object but can not instantiate children objects. when I reload the scene, Scene get reloaded with the object which was active when game started not with the object on which level failed.