Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions. Wa alaikum assalam wa rahmatullahi wa barakatuh. As to what follows: In response to your question, we say: If the illness was curable then making up for the missed fasts was not incumbent on the dead person because he died without getting a chance to make up for it. Likewise it is not incumbent on the dead person’s surviving children to make up for the missed fasts. A group of scholars have narrated that this view is the consensus of the scholars on this issue. However, if the illness was a chronic illness and continued until the person’s death and he did not feed the poor in compensation nor make up for the missed days, then in this case it is incumbent upon the person who is responsible for the dead person’s affairs, if possible, to take some money from the dead person’s estate and feed the poor in compensation for the missed days. Allah the Exalted said, “And upon those who are able [to fast, but with hardship] - a ransom [as substitute] of feeding a poor person [each day]” [al-Baqarah 2:184]. The person responsible for the dead person’s affairs can fast on his behalf if he made a vow to fast and died without fasting, or if the dead person was supposed to make up for a missed fast but he was negligent and died without doing so.