They both show up in Oneal District, Talbot Co. GA census for 1880. Marshall as head-of-house with his wife amelia, thier children and a Station? Mahone who is listed as his his brother-in-law. Which most probably means his wife was a Mahone. In the same year, in nearby Waverly Hall, Harris Co., Mariah Mahone a widow, is living with a Daniel and Lilli Silas and is listed as his mother-in-law. Could it be that Mariah was also Marshal's mother-in-law? Just a possibility to look into.