1870 Census of Bastrop County includes an Anna Lamaster, aged 40, born in MS. With here is "Rolf" (aged 16), Kathi, John, Thomas, and Chad. That's handwritten page 114. On the next page, handwritten page 115, stamped page# 474, is R. D. Lamaster, aged 17, with Cole, Anna, Chad, James, and Thomas.
It looks very much like the census enumerator hit the same house twice as Anna in the second house is aged 40.
So I would look for a Ralph D. Lamaster, whose mom was Anna. The name I give as "Chad" is indexed as "Charl". Rolf is indexed as "Polt".