I want to know: (1) If a man (A) kills (B), then can the family of (B) have the right to kill the man (A) or to take blood money? What is the amount of blood money to be given? (2) If (A) is not available, then can the members of (B) punish family of (A)?

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 is His slave and Messenger.

The guardians of the family members of the person who was deliberately murdered  have the right to kill the murderer and it is not an obligation on them to take the blood money. The evidence for this is the Hadeeth of the Prophet Muhammad who said: "If somebody is killed, his closest relative has the right to choose one of two things: either the Blood money or retaliation by having the killer killed." [Al-Bukhari and Muslim]

The blood money stipulated for premeditated and semi-deliberate murder is to be strict and heavy. Its amount should be one hundred camels: 25 she camels which had entered their second year, 25 she camels which had entered their third year, 25 she camels which had entered their fourth year, and 25 she camels which had entered their fifth year. This blood money should be paid at once, with no delay (please refer to the books of Fiqh (jurisprudence) for more details on this issue).

The family of the murdered person has no right to punish the murder's family since doing so is considered transgression. Allaah, The Almighty, Says (what means): {And no burdened soul can bear another's burden…} [Quran 35:18] Allaah also Says (what means) : {Whoso is slain wrongfully, We have given power unto his heir, but let him not commit excess in slaying.}[Quran 17:33].

Imaam Al-Baghawi said: "Ibn Abbaas said: The view of the majority of the interpreters of the Quran is that he : "It means that it is only the killer who should be killed by the person who takes legal retribution for the person killed". For in the Pre-Islamic period of ignorance (Jahiliyah), people were not satisfied with retaliating their killed ones by killing the killer himself; rather, they kill someone nobler than him.

However, retaliation should never be accomplished unless undertaken by a legal (Islamic) court. If such a court is not available, it (retaliation) should be referred to any Islamic authority specialized in looking after Muslims' affairs to solve the issue.

Allaah Knows best.