After my brother had previously performed Hajj for himself, he performed another Hajj on behalf of my deceased father. It is known through authentic Hadeeths that the one who performs Hajj without approaching his wife for sexual relations or committing disobedience will return as free from sin as the day his mother gave birth to him. It is also reported that the reward of an acceptable Hajj is nothing but Paradise. Would this reward include the one on whose behalf the Hajj was performed, meaning my father? Noting that he was known for his righteousness, faith and obedience but could not perform Hajj during his life.

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If a person died before performing a Hajj that was due on him or if there is someone who is unable to perform Hajj, then the closest of his kin should perform it on his behalf. Both the deceased and the one who is unable to perform it will receive the reward of Hajj, Allaah Willing. This is because the Hadeeths that encourage Hajj are of a general indication, which encompass the one who performs the Hajj himself and the one on whose behalf it is performed. Among these Hadeeths is the one that reads: "The one who comes to this House so as to perform Hajj and neither approaches his wife for sexual intercourse nor commits disobedience will be free from sin as the day his mother bore him." [Al-Bukhari and Muslim]

Hence, your brother did well when he performed Hajj on behalf of his deceased father as he is actually required to do so based on the Hadeeth narrated on the authority of Ibn ‘Abbaas who said that: "A woman from the tribe of Juhaynah came to the Prophet, sallallaahu ‘alayhi wa sallam, and said, "My mother vowed to perform Hajj but died before performing it. May I perform Hajj on my mother's behalf?" The Prophet, sallallaahu ‘alayhi wa sallam, replied, "Perform Hajj on her behalf. Had there been a debt on your mother, would you not have paid it? So pay the debt of Allaah as He Has more right that one should fulfill his obligations to Him." [Al-Bukhari and Muslim]

It is also narrated on the authority of Ibn ‘Abbaas that he said: "A woman from the tribe of Khath‘am came in the year of Hajjat Al-Wadaa‘ the farewell pilgrimage of the Messenger of Allaah and said, "O Messenger of Allaah! The obligation of Hajj is due on my father but he is a very old man and cannot sit properly on his mount. Will the obligation be fulfilled if I perform it on his behalf?" The Prophet, sallallaahu ‘alayhi wa sallam, replied in the affirmative." [Al-Bukhari and Muslim]

If your father did not perform Hajj because he was not able to, then he is not sinful, Allaah Willing.