Gift deed

My widow aunt (who have no child) had gifted her 1/7 equal undivided share in favour of me (21st May 2008)after execution a General Power of Attorney and an agreement(19th Apr, 2008) to our appointed developer. In the said deed my aunt was declared about the General POA and about the said agreement. Now the relation between my aunt and me is not good. In addition our one legal heir (out of 7 share holders) has claimed 600 sqft are after construction of the property and all of us are being agreed to give him that. Now the developer is preparing a deed for the 600 sqft keeping my aunt's name (who already gifted me her 1/7 share) and offering me to sign it for further process,but I deny to sign . Now my question is that, is it possible to prepare any deed by keeping my aunt's name (who is no more to the property) and I also offer to the developer, if you want to keep the name of my aunt the you also need to prepare another supplementary agreement with me in favour of the gift deed which was executed long before and its very well known to all of our share holders included the developer. But the developer is disagreed to do any agreement with me. So what will be my next step? Pl suggest me