You need original documents of title 

2( certified copy should be with seller 

3) if seller refuses don’t purchase the property 

They should provide you with certified copies of tge relinquishment deeds. That would be sufficient as long as a chain of transfer of title deeds/relinquishment deed can be traced. Certified copy is an authentic proof.

For precautions take a registered agreement between tge parties that what documents theya are submitting.

You have rightly stated that the registered relinquishment deed is part of the chain of title documents.

The sellers have no right to retain the registered title documents or the chain of title documents which form part of the original documents that have been handed over to the buyer at the time of executing a registered sale deed/transfer deed.

If at all the sellers want to use them for income tax purpose, they can very well obtain certified copies. The income tax department do not insist on original documents in respect of the subject matter now referred.

It is just a gimmick or that they are doing intentionally without knowing the consequences..

You can refuse to buy the property if they refuse to hand over the original documents atr the time of transferring the property by registered sale deed. 

DDA carried out substitution of title and executed conveyance deed on the basis of  un-registered  relinquishment deed . Registered  relinquishment deed registered  subsequently has to be handed over to the party in whose favor deed is registered. Under the deed family members are executants and you are claimant of  property. Registered  relinquishment deed is regularization of  un-registered  deed executed in 1999. It relates back to 1999 deed.  As the deed of relinquishment in favor of third party, it is  no more a family document . There is no such arrangement of giving an undertaking to produce a document  as when required by third party. Insist of original deed.

firstly i do not understand why the original of the registered deed would have to be submitted to DDA?

What will DDA do with the original ?

no point taking a certified copy since that you can any which ways apply from the sub-registrar's office and get as many number of certified copies of the deed as you may want 

the seller's contention that the registered deed is a private family document does not have any legal basis

when the property itself is being sold, where is the question of retaining the original relinquishment deed?

what will the seller do with the original registered document ?

it would have been understandable if the registered document was made in respect of more than one properties apart from the property being sold to you, in which event, for the other properties the seller would be justified in saying that he is entitled to retain the original since it also pertains to his other properties

but here the entire property is being conveyed to you so it but natural that all the chain title documents must be given to the purchaser by the vendor

there would be problems in the future when you go to sell this property as your buyer would require you to hand over all the original title documents 

so the seller's demand is not legal and is unreasonable 

you must insist for the original 

and if he refuses then you will have to rethink about proceeding with the transaction 

if you want this property anyhow then all i can suggest is to take an undertaking from the vendor that he will keep the original registered deed duly insured against incidents like fire and will also not create any third party using the original document and will give you the original as and when you require against a proper receipt and after the work is done the original can be returned to the vendor

the above is only as a stop gap arrangement

the more prudent thing to do would be to insist upon handover of the original since the purchaser after sale of the property has no business to keep any original title documents with him

The buyers are right in insisting on the relinquishment deed as it forms an integral part of the chain of documents. If it finds a place in the Encumbrance Certificate, you can easily get a certified copy from the land registry concerned.

It's sufficient along with indemnity bond and other documents of not having the original Relinquishment deed from the seller

Dear Client,

                 Unregistered relinquishment deed is not a valid deed in law and can't be contested in court. As far as any transaction to immovable property.A relinquishment deed is created and registered to enable the co-owners to legally transfer their share in the property to another co-owner.The term relinquishment refers to the abandoning and surrender of the rights, title, and interest, by one co-owner of property for the other co-owners. The consequences of relinquishment of one co-owner’s share in property are the enlargement of the shares of the other co-owners.

If you are planning to sell a property , the documents are very important.A property with clear documentation and title commands a higher price in the market.The original conveyance or sale deed from the previous owners of the property is needed. If you have lodged the original deed for registration with the registrar, you need to provide a copy of the conveyance deed or sale deed along with a photocopy of the receipt from the sub-registrar where the documents have been lodged for registration.This traces the ownership of the property. Missing documents in this chain can raise a red flag. A property with clear documentation and title commands a higher price in the market. The chain of previous agreements with past owners in original with original receipts of registration or the original letter of allotment issued to the first owner by the development authority is important.

Even if you are getting the certified copies of the relinquishment deed that will suffice your requirement as to the completion of the chain of the title document. 

Certified copy means that you are given the true and correct copy of the original document authenticated by the registering authority which is a conclusive evidence. 
Either way you can attach the certified copy in the chain and it will be valid. In alternative get the affidavits from the seller that they undertake to provide the original document as and when required for the property proceeds later on. 

In case you require my assistance in the matter, i can be contacted through my google profile. 
Link of the same is attached for your reference as:

https://g.co/kgs/ZMWUyY

Your kind review will be appreciated. 

- An unregistered relinquishment deed is not a valid deed in law and can't be contested in court.

- Further, any transaction to immovable property shall be valid only when the deed executed, is registered by properly paying stamp duty and the registration charges.

- Since, the said relinquishment deed was not registered from the office of the Registrar in Delhi, then the legal heirs who has executed the same , may claim the property. 

- However, if the registration is taking place after the execution of conveyance deed , then this deed cannot be accepted for the purpose of transferring ownership in the name of new purchaser. 

- The seller should handover all the property documents to the purchaser, and also bound to give the original of all the property documentary chains to you. 

- NO, only in the event of missing the document , its certified copy having value in the eye of law, and further it may create problem for you at the time of selling the property. 

- The seller having no legal right to withhold any property documents in original after selling the property . and bound to handover the same at the time of transferring property to purchaser.