Is unregistered partition deed valid or not?

Hi All, My father has received his share of immovable property from his father as a result of partition of my grandfather's property amongst his sons. The property was divided as agreed by all the brothers which was documented on a stamp paper. All the parties of interest(my father and his brothers) have their consent to the partition which was done in 1989 and duly signed by everyone including witnesses on the stamp paper. However this partition deed is not registered with sub-regstrar. There are no conflicts or issues regarding the partition or the share amongst the brothers or their heirs so far and hope there will be none. However we are now planning to demolish our share of property and re construct a new building; i am only worried if it is sensible to do so? As the partition deed is not registered, if it may lead to conflict in future? Is it mandatory to register the partition deed or can we proceed as is? Is it legally possible for any of my father's brothers or their heirs to claim part in this property in future? In case if we wish to sell this property, will it create any problems as the partition is not registered? Finally if we alone want to register this partition deed, can we do so without any other brother being present? ( A couple of them are dead and another couple live abroad, it is almost impossible to get everyone to agree to do this; although there are no conflicts with regards to the properties) Greatly appreciate your advice.