1. sharing agreement between landowner and builder is not required to be registered
2. ask builder to take NOC from all 6 landowners and annex it to your sale deed
3. in the alternative all the 6 landowners can become confirming parties in the sale deed to be executed between you and the builder
there is a correction to my response as below:
ask the landowner to take NOC from the other 5 landowners and the builder and annex those NOCs to your sale deed with the landowner from whom you are purchasing the unit
or in the alternative you can have the other 5 landowners and the builder be confirming parties in the sale deed between you and the landowner
apologies for the previous reply. Except for the modification as above, the response remains the same