Not theoretically impossible but Walter was not likely to have two brothers named James. It is quite possible, however, since at least four brothers and two sisters made the trip to N Texas from Virginia, that collateral lines came with the wagon party as well, especially any children of the two older brothers who died in the Civil War. It may be that your earlier James A Alexander was one of these nephews. If there are Virginia connections, it is worth pursuing. If by any chance you are living in the Ft Worth area, you have access to the Southwestern repository of the National Archives. A look at the census figures for Alexanders in Tarrant Co from 1870 thru 1920 might clear up the relationship very quickly. I would certainly be interested in anything else you might find out on any Alexanders living in Tarrant County during the period of which we speak.