Looks like Seward was counted twice on the 1930 census.
1930 census Brownville, Cameron Co, TX:
Carney, S.M., h, 38, m @ 16 yrs of age, b IN, US, US
" Refugio, w, 37, m @ 15 yrs of age, b TX, TX, TX
" Luis, s, 6, b TX
" (Telora ?), d, 4, b TX
Garcia, Emilio, stepson, 9, b TX, MX, TX
[S.M. is a soldier.No house numbers, but it looks like they live on street named Monroe.]
Carney, Seward M., h, 38, m @ 27, b IN, US, US
" Cuca, w, 37 m @ 26, b TX, TX, TX
" Emale, s, 10, b TX
" Lusse, s, 5, b TX
" Lola, d, 4, b TX
[Note age married is supposed to show age when married first time, looks like on the second entry they are showing their ages when they married each other.From the name of the stepson, it is obvious wife was previously married, so Seward also may have had a previous marriage.]
A copy of Seward's death certificate should show the names of his parents.Accuracy only as good as the knowledge of the informant.On the other hand he filled out his application for his Soc Sec card and that application should show the names of his parents, his residence at time of application and other data, too.
Happy Hunting (^_^)