Your interest in the Alexander Family and its connection to my Kerfoot Family is part of whole that I am not going to trace.
I have a James Alexander as follows:
1. Wm. Kerfoot (said to be the emigrate) m. Mary Margaret Carter (name from family bible, unable to comfirm). They had seven children.
2. Sarah Kerfoot b. 1772 m. Wm. Alexander, they had eight children: Sarah K., Wm., Matthew, Hiram, Elijah, Margaret, John & your James.
3. James Alexander m. 27 Dec 1821 1821 Frederick Co. VA toJane Peyton
I forget, but I might have put some posting about this family group on my cousins Michael L. McKay's web site. Believe something about slave division of Sarah Alexander.
The answers to your questions will be found I am sure among in Frederick Co. VA Land Deeds.
My cousin Michael L. McKay has a web site concerning the family of Robert Mackay of the early Shenandoah Valley and allied families, one of which is Kerfoot family.
I believe Michael has a link to the site where a web master has the entire Kerfoot Book on line for the taking. It might also have Alexander information.
You might want to put a posting on Michael's site under "Discussion Forum", perhaps others are interested in the Alexander Family. As I am doing a quick read through of Frederick Co. VA Land Deeds if you want me to look out for information about your branch of the famiy, better put a query on Michael's page, or I will forget.