Do you have their Choctaw Nation Census Card from the Dawes records? It should tell you who John's parents are. If you don't have the card, do you have his roll number? From the roll number you should be able to find the card number.
Ok looked up some info: Your family is listed on card #3525
John's father is listed as Dan Owens
Kate is listed as IW (Indermarried white)