Funny you mention that, Lisa. I've had the exact same issue. My great grandfather, John Wood Ellis, apparently enlisted in the 7th Battalion in Spring of '62 while at least two of his brothers joined Co. H of the 8th. There home was roughly between Meridian and Quitman. John was a little younger than his two brothers in the 8th, so that may have had something to do with it as Co H of the 8th was formed a year earlier, I believe. Seems like in our family history somewhere, that there was some kind of southern draft law put into effect in '62 and once he was 18 he had to enlist.
Further confusing things is that there IS a J.W. Ellis on the rolls of Co G of the 8th, but in looking up service record cards for that J.W. Ellis, all I could find is that he was a Sergeant and was apparently captured at Gettysburg. I don't think that's my guy because he certainly couldn't have been at Gettysburg and Vicksburg, which I think were at the same time. Also, and someone correct me if I'm wrong, but I didn't think the 8th Mississippi was AT Gettysburg.
Getting back to the original issue, though. Lisa, could your relative in the 7th Battalion have been a little younger than his siblings? Maybe the family thought he was a little too young in '61?
James, tell me a little more about what you found at the courthouse in Quitman? I may just have to make an excursion over there one day to dig around.