Buy property from NRI widow

Hello- We have liked a property that we are contemplating to buy. The seller is a widow; she has 2 adult kids. All 3 of them are NRI. Only the lady has come down to India for a month or so to sell the flat, her 2 kids are still abroad. The property was originally bought from the builder in joint name, the lady being the 1st owner and her (expired) husband the 2nd owner. Society Share certificate has only her name (the back side of the share certificate is empty). 1. Shouldn't the share certificate have to have 2 names since it was purchased in joint capacity? Could it be that after her husband death she got the property transferred to her own name and the society issued her a new share certificate in lieu of the older one? 2. Will we need to obtain any kind of NOC from the kids? P.S. Kids are not present in India physically at the moment? Will the kids have to come down to India to do any kind of paper work for this deal? Do we need any kind of PoA from kids? Just want to make sure there should be no ancestral kind of claim in future from the adult kids as the father has now expired. Basically I am totally confused how to proceed with the deal. Please help, urgent. Simran.