Praise be to Allah.
If your father was able to make up the days that he owed from the previous Ramadan, but he neglected to make them up before the Ramadan after which he died began, then it is better for you if one of you fasts and makes up these two days that he owed, because the Prophet (blessings and peace of Allah be upon him) said: “Whoever dies owing fasts, his heir should fast on his behalf.” Agreed upon. And if you feed the poor on his behalf by giving a saa‘ of the local staple food, which is equivalent to approximately 3 kg, that will be sufficient.
But if before Ramadan he was unable to make up the two days because of sickness, then you do not have to make them up or feed poor persons, because he was not negligent.
And Allah is the source of strength; may Allah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote.
Standing Committee for Academic Research and Issuing Fatwas