Can are grandchildren claim grandfather's property after parents divor

My brother (18years) and I (21 years) live with my mother overseas (Australia). My father and mother are divorced (2016). When we were minor our mother started a case in court to have our names registered in my father's side of the property. But the opposition lawyer says that because my father is not included in the will of my grandfather, we do not have a claim to the property. My grandfather has 3 kids, my father is the middle one. Do my brother and I have a claim at the family property, can we fight this?