Can husband write a power of attorney after wife's death, for property in the name of his wife?

Hi, I have purchased a property around 7 years ago but was not having much knowledge about the legality and documentation process at that time. I have purchased a plot from a Mr. X who had POA (power of attorney) given by the husband (Mr. Y) after wife's death. The property was in the name of his wife. In POA agreement, it is written that husband (Mr Y) was the sole and only legal heir of the property and therefore he is giving POA to Mr X. I have purchased the plot from Mr. X through this POA and got property registered in my name. I had taken Bank loan from LIC HFL. I have got all the chain documents of the property and also gave "Jahir Suchna" in English as well as Hindi newspaper at the time of purchase. Now after these many years, I once again looked back into the property documents and I feel there exist a problem in POA. As per my understanding (which i got now) that after wife's death property is equally divided among all the legal heirs (husband + children). But in POA, it is written that husband (Mr. Y) is the sole and only legal heir and therefore writing POA in favour of Mr X. Though after so many years (7 years), there has been no claim on the purchased property from any person. Can you please give your views whether POA written by Mr. Y in favour of Mr. X is valid document? Also, I don't know if there were any children of Mr Y or not? And now the matter is very old, I could not trace it either. What is the best way to not get into any trouble in future? Please provide your valuable feedback. Thanks, Nikhil