See the property was given as divorce settlment and has status of self acquired property it is immaterial that it was acquired from your father's earning as the property of hindu women is her sole property and she can gift will sale according to her wish so the will made by mother is valid and you don't have any right on property
In case there was no will you all had equal share since there is will the property shall be distributed as per will and you have no right even if you challange it the suit will get dismissed and there shall be no profitable outcome.