Buying of undivided property.

I have bought an apartment in year 2011. The case is as follows. After the death of mother two son and one daughter became the co-owners of the Property. They decided to use it for promoting apartment. After completetion of the project they were provided with apartments in the same floor eg. flat 3, flat 4, flat 5. They mutated thier names in the municipal corporation against the possession letter. They dont have any Partition deed. They have been alloted separate asssese number for each property.But since they dont have any partion deed corporation declared it as a undivided property, which is not .

They all have been alloted separate apartments. In the year 2011 the elder brother sold his portion to me. I was not aware of such matter even the lawyer we appointed was also not well versed with this scenario. By the virtue of possesion letter they all are enjoying their portions. Even the property was registered properly but when we went for mutation we are unable to do so. The reason is that they dont have any partion deed. Now the junior brother is totally debt ridden and in no way is able to pay any money for partion deed. In this scenario what is the option that we can opt so that mutation is done in our favour.