Parking allotment in apartment

I have purcased flats in Chennai 2015, but the builder has not allocated exact place of carparking to me, since i purchased. Apartment has 5 flats, now in 2018 5th flat was sold and rest of owners asked builder to mark car parking for all owners. But Builder is trying to give previlage to the fifth owner in car parking and also the fifth owner saying, builder sold his flat by stating independent covered car parking will be allocated to him so he required enough space for his big size car. Incase, as such if the builder is going to allocat to him, one amoung other 4 owners will get very less size car parking and cant able to park even very small size car. so now all other 4 owners asked builder to split car parking in 5 equal size, same builder was accepted and the parking was marked. But again the 5th owners is not ready for equal size parking. Note: Parking mentioned as per construction agreement are For all 4 owners, Common car parking is provied (Front and back) For 5th owner, independent covered car parking in the stilt. Clarrification required on 1.All 4 owners are formed as a socity and along with builder, we splited the parking in 5 equal size and made rest of parking as common area, whether this will be legial? 2.Whether 5th owner can go for case on builder to allocat parking as mentioned in his agreement? 3.What will be the result of all 5 owners are taking legal action on builder? whether 5th owner will have added advantage than others?