society Redevelopment area issue

In our society out of total 18 flats , 9 members have enchored upon and built 2 rooms extra as unauthorised construction years back and 9 members have not done even an inch unauthorised construction , but know as the society is going in for Redevelopment process , these 9 enchroached members are asking for excess area as per their current area and not as per original area as given by builder as per sanction plan which is indirectly affecting the extra area of honest 9 members , what is your advice