James Leith born in Scotland in 1685. He died in 1740 in Shenandoah County, Virginia. Researchers name two wives and confusion begins there. One wife named is Helen Farquharson born in Scotland around 1695. The more accepted wife is named Ann French born in 1681 in Woodbridge, Middlesex County, New Jersey. She died in 1751 in Frederick County, Virginia. They married in Woodbridge June 29, 1711..
James Leith would have immigrated from Scotland to the colonies arriving in New Jersey before 1711 when he married..
The family research I reference by Virginia Erwin Page works with the birth of George between 1715-1720 and would then be the child of Ann French. James died before his wife, Ann French, thus a second wife had to be someone he married while he was quite young.
http://trees.ancestry.com/tree/47239187/person/6947289965/mediax/1?pgnum=1&pg=0&pgpl=pid%7CpgNum