A. In your case, there is no clinching proof to establish ancestral property. In order to qualify any property the test to be identified as Ancestral property it should be owned by the great grand father followed by grand father, father & present generation all in this linear generation living & enjoying the property.
B. In short , firstly,this property should be four generation old, secondly it should not have been divided by the users in the joint Hindu family as once a division of the property takes place, the share or portion which each Coparcenar gets after the division becomes his or her self acquired property.The right to a share in ancestral or coparcenary property accrues by birth itself, unlike other forms of inheritance, where inheritance opens only on the death of the owner.
C. Your father can transfer his share to anybody without obtaining consent of the all apparent legal heirs. Hence, your sisters have no right to claim partition over the Father's property.For your more information, Property inherited by will and gift are not ancestral properties.
D. And to add a further twist,self acquired property can become ancestral property if it is thrown into the pool of ancestral properties and enjoyed in common.