Have you tried to get a copy of Sam's death certificate?
If the informant knew Sam's parents' names, he/she would have listed them on it. You can obtain a copy through Virginia Department of Health, vital records. If you google it, the site should come up. I have listed for his death date May 28, 1946.
Have you tried searching from the other side of the ocean?
I found (on Ancestry) where Sam and his brother came in on same ship "Batavia" from Hamburg, Germany, departure date: 29 Mar 1907. Arrived in NY., 14 April 1907. Anna apparently came in 1909 with daughter - I didn't look up her ship etc. Sam's Naturalzation papers from 31 Mar 1920, gives the immigration date as/about 26 Feb. 1906 - NY from Hamburg and can't make out the name of the ship. You can find the record on Ancestry if you don't have it.
Good luck - Regina