Is it obligatory to take the blood money from the person who caused the accident in which the mother and two brothers died, or is it permissible to pardon him, especially given that the perpetrator was driving against traffic at a speed of 160 km/h, under the influence of intoxicants, and that the father and the questioner are in debt?

Deaths resulting from accidents are considered involuntary manslaughter. The 'Aqila (male relatives on the father's side) are responsible for paying the blood money (diyya) for all deaths, unless the victim's family pardons the perpetrator. The expiation (kaffara) for each victim is to be paid from the perpetrator's own wealth. Intoxication does not waive the diyya or the kaffara. The victim's family and heirs have the right to claim the diyya or to pardon it, and pardon is better if it does not lead to harm. The right to pardon or demand the diyya belongs to all heirs of the deceased, not just to one of them exclusively.