Bruce,

I'm pretty sure that Marshall McCord Foster (who seems to have gone by Marsh) was one or two years older than Emory. That is reflected in the 1860 Johnson County Census. http://files.usgwarchives.net/mo/johnson/census/1860cens.txt Also confirms the positions of McCown and Marsh. The following genealogy page seems to have good date/name information, searching under Fosters: http://www.martisgenes.info/i27.htm#s1208.

I haven't had a chance to read more of that Johnson County history yet. I found the pdf of it this morning while I was trying to get a handle on the family. There was a lot in there about Melville post war from what I recall of a quick search.