Is it obligatory to fast two months for each person, or for both of them, or to pay the blood money, or nothing, concerning the death of two Christian individuals in a car accident in which the Muslim was not the cause?

If the driver abides by traffic laws and safety procedures, then there is no blood money (diyya) or expiation (kaffara) due from him. However, if he is at fault, then he owes two diyas for the two individuals. The diyya for a Christian is half the diyya of a Muslim according to the Maliki and Hanbali schools, and one-third of it according to the Shafi'i school, while it is a full diyya according to the Hanafi school. Expiation is obligatory for each of them according to most scholars, even if the deceased was a disbeliever.