You probably have this information already, but the 1930 census shows them living in Clinton, Elkhart County, Indiana.Robert was 26 (born 1904), had married at the age of 20 and he and both of his parents were born in Indiana.His wife, Eva was born 1905; she and her mother were born Indiana and her father born Arkansas.They had a daughter Virginia, age 5, and a son Dannie.
The Social Security Death Index has Robert residing at 46525 Goshen, Elkhart County, Indiana when he died.He was born December 19, 1903 and died November, 1976.
I couldn't find Robert in the 1920 census.He wouldn't have been married at that time.
The 1910 census shows a Daniel Lewallen Lewallen living in Jackson, Elkhart County, Indiana.He was 48 (1862) and he and both of his parents were born Indiana.His wife was Lena age 45 and she and her father were born Indiana and mother in Pennsylvania.Their children were Clyo age 18, Daniel R. age 16, Frank R age 5, Dortha M. age 4, and also living in that household was Rebecca Wyland age 74 who was born Pennsylvania and both her parents were born Pennsylvania.
I point this census out because of where Daniel lived - Elkhart County, plus (1) Robert and Eva had a son named Dannie (short for Daniel) and (2) the Frank R. was the right age to have been Robert.
The 1900 census shows Daniel and Lenia in Tippacanoe, Kosciusk County, Indiana.Daniel is shown as having been born December 1863 in Indiana and both his parents born Ohio.Lenia was born Indiana 1865.Her father was born Ohio and mother born Pennsylvania.they were married 1885.Others in the household:Verney age 11, Gregory 13, Clyo 6, Danny 4 and Sarra Grider 30 born MN, father born PA and mother OH.
The 1880 census shows the Daniel's family in Tippecanoe, Marshall County, Indiana.David Lewallen age 32 (1842)born Ohio, father born New Jersey and mother born Pennsylvania.Elisabeth 37 born Indiana, father born Ohio and mother born Pennsylvania.william 19 born Indiana, Daniel 17 (1863) Indiana, Jane 14 Indiana, Aville 13 Indiana, and Sarah 4, Indiana.
Hope the foregoing helps some.I can't say for certain this is your family If you haven't obtained a copy of Robert's death certificate, I'd suggest you do that because they often contain very helpful information such as the names of parents.