The VA Forehands are not "my" Forehands, but I do have some info that should help you on your way to tracking them down.
Warning!I have not personally verified any of the following info.This is just data that I have pulled from Ancestry.com and FamilySearch.org (the LDS site).
The John Forehand who married Rebecca Campbell is often given as the son of Darby Forehand of PA (b c 1735, died 27 Dec 1777, Valley Forge, PA).Besides John, Darby is credited with at least one other son, William.
The tricky thing about tracking down the Rockbridge co Forehands is that the spelling of the last name is fluid, to say the least.Forehand, Forehan, Forean, Forren are the most common variants for the 1800's. I won't burden you with all the details in this post.However,I will be happy to send you the file I have if you are interested.