Ruling on a father who accidentally threw his son off the roof and the son died

Q: A long time ago, my father A. H. S. A. Caused the death of one of his sons. While the father was standing on top of the house holding a rough piece of wood with many branches to throw it into the yard, (Part No. 21; Page No. 324) my brother came quickly to watch the piece of wood falling. One of its branches hit him causing him to fall from the top of the second floor and he died instantly in the yard. The accident took place in the southern region. My father died fourteen years after my brother's death. He did not know he had to expiate for it because he did not intend to kill his son and did not know he was there at the time when he threw the piece of wood.I am concerned about expiating for the sin of my father if he is accountable for this. I am confused regarding what I should do. Therefore, I seek your advice and guidance on what to do to expiate for my father's deed, if he is accountable for this accident.

A: If the reality about your father's deed is as you mentioned, he had to offer Kaffarah (expiation) for involuntary manslaughter, which is freeing a Muslim slave. If he was unable to do so, he had to fast two successive months, according to the Saying of Allah (Praised and Exalted be He): It is not for a believer to kill a believer except (that it be) by mistake; and whosoever kills a believer by mistake, (it is ordained that) he must set free a believing slave and a compensation (blood-money, i.e. Diya) be given to the deceased’s family, unless they remit it. To His Saying: And whoso finds this (the penance of freeing a slave) beyond his means, he must fast for two consecutive months in order to seek repentance from Allâh. And Allâh is Ever All-Knowing, All-Wise. Surah Al-Nisa', 4:92 (Part No. 21; Page No. 325) Since your father died without doing what he had to do, his heir has to purchase a Muslim slave from his estate and free him. If the estate can not afford this or there are no slaves, it is desirable that his inheritor should fast two successive months instead of him according to the Saying of the Prophet (peace be upon him): If anyone dies in a state (that he had to complete) some days of fast, his heir must fast on his behalf. (Agreed upon by Al-Bukhari and Muslim). May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.