The family members were travelling from his burial when the accident occurred in Nakuru.
They include Oriaro’s cousin, the wife and their child who were traveling from Siaya after the burial of Oriaro who was found dead in a swimming pool in Mombasa recently.
Police have named the deceased couple as Patrick Ochieng’ and Rose Akoth, but have not released the child’s name.
Rift Valley Traffic Police chief Mary Omari says the couple died on the spot while the child was pronounced dead on arrival at the Rift Valley Provincial General Hospital.
Police had announced that they were investigating circumstances under which Oriaro drowned in the pool of a Mombasa hotel after the Law Society of Kenya’s Annual General Meeting.
His family complained of foul play.