Flat owner's association

I have moved in to a new apartment. The building has stilt plus two floors. Ground / stilt is car park. Total number of flats promoted - 6. Two are retained by promoter Of the balance four I have purchased two and asked the builder to join the two flats by opening the common wall and providing a door instead. This has been done during construction stage itself Since the approval is for six flats and considering the future possibilities I have registered the property as two but in one name (I am power holder). Builder is a relative of promoter.. I am the first to move in when handing over is not completed (even today it is not) Of the balance two one is sold to another relative of builder. The second one is taken by suppose to be a nuetral person. We formed an association, yet to be registered and building yet to be handed over by builder. Builder vanished one day forcing us to take care of common maintenance. Others in the premises ask me to pay maintenance for two flats - but my flats are joined and only three of us live. In other flats more people live. Flats are not of same size (two are smaller and I own one and the suppose to be neutral person owns the other). Dividing the common maintenance by five flats or dividing based on the number of people live and share the common areas, power including lift and water. Why should my flats be considered as two by others as we have combined it as one. Any guidelines on this issue. Building is in Municipal area, out of Chennai corporation limit. Thansk in anticipation