Is it permissible for children to fast on behalf of their father to make up Ramadan?

The questioner : Shaykh, may Allah preserve you. This is a woman who called to inquire about two questions. She says her father passed away five days before Ramadan, and seven years prior he had not fasted Ramadan because he was suffering from diabetes, high blood pressure, and some other illnesses. Do they make up the fast for him? Do the family members fast these days on his behalf?

The Shaykh : We must ask about his illness: was it an illness that was not expected to end at that time? If it was an illness that was not expected to end, his obligation is to feed the poor; they feed one poor person for every day. If it was an illness that was expected to end, and he recovered from it, but he was negligent and did not make up the fast, then they fast on his behalf. It is permissible for one, two, three, four, ten, or thirty people to fast on his behalf. There is no harm in their fasting on the same day. For example, if he had six sons and each of them took five days, and they all fasted them within one week, there is no harm. The important thing is that the distinction I mentioned first must be observed: if he left off fasting due to an illness that was not expected to end, his obligation is to feed the poor, and they do not fast on his behalf. If he left it off due to an illness that was expected to end, and Allah healed him from it, but he was negligent and did not fast, then they fast on his behalf.