A friend of mine told me that his parents married in Ramadan. His father erroneously believed that fasting was not obligatory for him and his wife since they were newlyweds. Accordingly, they did not fast the entire month of Ramadan in which they got married. The mother stated that she had made up the days owed, but the father died before doing so. Can the son make up the missed fast days on behalf of his father? Are there any other requirements?

Assuming that the man mentioned broke his fast by eating and drinking, and made no intention to fast to begin with because of his mistaken belief that he did not need to fast because he was a newlywed, the ruling in this case is that he should have made up the missed days, though atonement was not necessary. It is true that he had sexual intercourse with his wife, but he did not make the intention to fast to start with.
His son must feed a poor person for each missed day of fasting. This means that he has to feed 30 poor persons on behalf of his father.
And God Almighty knows best.