Purchasing a property that is presently in the name of a deceased person

I plan to buy a house (low rise apartment) in Gurgaon, along with my father (sr. citizen) as a co-owner. We will be using funds from the sale of property in our hometown. The property that we have shortlisted, belongs on paper (allotment letter and builder records. The house is currently not registered in their name and a Registry is yet to be made) to a person who unfortunately is no more. This person is survived by his wife, parents, and two children (both minors). The representative from the seller side has told us that they will get the property papers transferred to the wife of the ex-owner, with the help of a Legal Heir certificate. According to them, the legal heirs in this case would be the wife of the deceased and their minor children. Basis the legal heir certificate, they intend to first transfer the allotment letter in favor of the wife (new owner) and then get the registration certificate made too. Once this is done, they intend to sign the "Agreement to Sell" with me and my father, and later we can use this Agreement and the new registration deed (in the name of the wife of the ex-owner), they tell me that we can sign the sale deed and get the property registered in mine and my father's name. As this is a major financial deal for me, I don't want to just go with what the seller and the property broker is telling me. Plus, I have negligible knowledge of law, so wanted to be doubly sure. I want to see if what the plan above is, per the dealer and the ex-owner's wife, is good from a legal standpoint. I don't want to invest in such a property where after a while I get into any legal issue on the legal heir side or any other problem. I would request any help from any of your learned lawyers here on the forum.