Is an expiatory fast (kaffarah) or something similar obligatory for a man whose wife and sister died in a car accident he was driving, and is he obliged to marry after his wife's death?

If the driver who caused the accident took all safety precautions and was not negligent, then he is not required to offer expiation (kaffarah) or pay blood money (diyyah). However, if he was negligent in taking safety precautions, such as driving while needing sleep, or neglecting to check the tires, or violating traffic rules, then he is required to offer expiation and pay blood money. In this case, if there was no negligence or shortcoming on the part of the man who caused the accident, then there is no expiation or blood money due from him. But if there was negligence or shortcoming on his part, then his 'aqilah (male agnates) must pay the blood money for his sister and his wife, and he does not inherit anything from them. He personally must offer expiation for each of them.