Grandmother wants all the property of dead grandfather in 2005

My grandpa deceased after 2005 ,my aunt that is my father's sister was married to grandma brother Now my aunt, grandmother all want all properties themselves leaving my father None of the assets were self earned by my grandfather all are ancestors property,a handwritten partition happened on 1998 all signed but we have not registered it Now will that document be enough for fight in court or we should give some share to my aunt All the benefits for last 29 years wer enjoyed by aunt only not by us