First, please get all the title documents examined by a competent lawyer to ensure that the title of the vendor is clear, absolute and marketable. Check the society's bylaws too to ensure that there is no clause restricting sale and/or subdividing the existing plot. Afterwards, you may ask the vendor to execute two separate sale deeds and register them in the respective buyer's names. The original sale deed in the name of the vendor will be with one of you and the other will hold a certified copy. In the sale deeds to be executed by the vendor, suitable narrations to this effect should be made.