On the death of your maternal Grand Father, the property will devolve upon your Grand Mother, your father, your two uncles and 5 aunts (including the deceased) equally. The deceased aunt share goes to her children. Totally there are 9 legal heirs (including your grand mother). Hence, by above equation, your father will get 1/9th share. You can claim your right from this 1/9th share only. Likewise your uncles and aunts and your grand mother will get 1/9th share each.
You have not stated that the NOC is registered or not. Assuming that it is not registered, the NOC you were referring is invalid in the eye of law. It will not be taken as evidence in the court, since it is not registered in the sub registrar office. Hence, do not worry about that.
If the NOC is registered, only 3 sons and Grand mother can claim and the daughters (aunts) will not get any share in the property.
You or your father or any aggrieved family member can file a partition suit against the other members. The fee will be very nominal around Rs. 200/- only.