The Koch brothers are not Jewish. They are descended from William Ingraham Kip, a Protestant missionary who traveled to California in 1853 and was elected California's first Episcopal bishop in 1856.
Kip's granddaughter Mary Burnet Kip was the mother of Mary Clementine Robinson. Robinson married Fred C. Koch, and the two had four sons: Frederick R. Koch, Charles G. Koch, David H. Koch and William I. Koch. When news organizations refer to "the Koch brothers," they typically mean Charles and David, the two still associated with Koch Industries. Politically, the Koch brothers give large amounts of money to evangelical Christian and conservative Catholic groups.