My nephew is 5 and niece is 3 there parents abuse them mentaly and phisacally I want to adopt them but do not know how. There parents do not want to give them to us and would rather them go to a foster hom then be with us. What do we do can we fight for custody?

First, you report the abuse to family services telling them that you are willing to foster them with an eventual goal of adoption.

Unless you can prove the abuse you stand no chance of getting anywhere.