I have located a petition to the court addressing the homologation of the estate of Marsden Campbell, the father of William Simpson Campbell, James G. Campbell, Marsden Campbell, et al. dated May 23, 1860.

I believe it can be considered the "proof" of kinship we were looking for.

Marsden Campbell (Jr.) died intestate on December 8, 1857. At the time of Marsden's death, only William S. Campbell had attained the age of majority, that is, over 18. James Green Campbell was a few days short of his 18th birthday, and the rest of the children including the Civil War Marsden were younger still. It took until May of 1860 to finalize the settlement of the estate.

The quote from the document is as follows:

"Wherefore the premises considered petitioner prays that William S. Campbell a major heir of the said Estate and residing in the City of New Orleans and Mary B. Campbell surviving widow of the deceased as partners in the a_________ (Illegible) and James and Robert Benguerde as under tutor of the minors James Campbell, Fanny Campbell, Mary Campbell, Marsden Campbell, Annie Campbell, and Lucius D. Campbell residing in the Parish of St. Landry be duly cited to appear before Your Honorable Court to show cause if any they have against the homogation prayed for herein _____________ (illegible)the ____________ (illegible) of petitioner as administrator aforesaid; that said account be homologated, petitioner as administrator cancelled and that he be authorized to pay over ___________________________________________ (missing) and for general relief."

This document connects the names of the three brothers, William, James, and Marsden.

If you provide me with your current email address, I can provide you with a scan of the document for your review and a transcription as well.

David