Must the heirs of a deceased person who was unable to fast Ramadan due to surgery, and then passed away after Ramadan, make up the fasting on his behalf or feed a poor person for each day?

If a sick person dies immediately after Ramadan (definition), and their illness was continuous, preventing them from making up the fasts, then there is nothing due upon them. However, if they were able to make up the fasts but did not, then a mudd of the staple food of their country should be given as charity for each day. It is also recommended for their guardian to fast on their behalf, based on the Prophet's (peace be upon him) saying: "Whoever dies and owes fasts, their guardian should fast on their behalf."