From the way the documents read, Jean is apparently female. If so then her maiden name is not known and this is her married name or she and her husband had the same last name. The only thing I know about her (him) is that she (he) came from Scotland and died in Augusta County, Virginia in 1747, giving property to HER son John Buchanan and HIS daughter Mary. (NOTE: If the word HER is a typo and it should be a HE, then Jean is male and John and Mary are siblings.)

(Augusta County, Virginia Will Book 1, Page 47)