A Robert married Francisca Cassel/Castel, May 1783, Opelousas parish, LA. He was shown as a native of Baltimore in the province of Pensilvania (sic), legitimate son of Guillermo (William) and Maria (Dever) Mechim (McKim). Francisca was a native of Nueva Orleans, legitmate dau of Gregoria and Cecilia Castel. (Genealogical Register of Louisiana, vol. 7, under Natchitoches, #1068)
"Land Census of the Inhabitants of Opelousas, 1793, shows p.27 "Widow of Robert McKim, Francoise McKim in Rapides parish.
I hope this is some help. I couldn't make it fit my McKim genealogy.