Christopher Langan

John Gibbons Langan is a stepfather only.

https://en.wikipedia.org/wiki/Christopher_Langan

Christopher Michael Langan (born March 25, 1952) is an American horse rancher and autodidact who has been reported to score very highly on IQ tests. Langan's IQ was estimated on ABC's 20/20 to be between 195 and 210, and in 1999 he was described by some journalists as "the smartest man in America" or "in the world".