Is expiation (kaffarah) and blood money (diyah) obligatory for someone who lost control of his car, leading to the death of his son and injury to himself? What is their amount, and to whom are they paid?

Your brother caused the accident, and it resulted from his action. Therefore, he is liable for the blood money (Diyah) and expiation (Kaffarah). This is considered an unintentional killing, and he is absolved of sin. However, the right of Allah regarding the expiation and the right of the child's heirs regarding the blood money remain. If the heir forgives, then only the expiation remains, which is fasting for two consecutive months.