Is it permissible to give expiation (kaffara) to needy relatives such as a son, and what are the implications for someone who issued a fatwa permitting this, and then it became clear that their fatwa was incorrect after the expiation was given?

It is not permissible to give expiatory payments (kaffarat) to one's ascendants (parents, grandparents) or descendants (children, grandchildren), because their maintenance is obligatory, and they are therefore self-sufficient by it from the expiation. This is to prevent the cancellation of two obligatory rights with a single sum of money. This ruling is not exclusive to zakat (definition), but applies to every obligatory charity; it is not permissible to give it to them, such as expiations, sadaqat al-fitr, and vows. The purpose of expiation is to make the one performing it feel the pain of spending a portion of their wealth as an expiation for a sin, and this meaning is not achieved if they feed someone whose maintenance is obligatory upon them. If a woman gives the expiation to her son, it is not sufficient for her, and she must give the expiation to its rightful recipients, because it is a debt upon her that is not discharged except by fulfilling it. Furthermore, according to the majority of scholars, giving the monetary value for expiations is not sufficient.