Since one of his addresses was in Knoxville, here is a Robert Martin in Knoxville in 1940:
(There are 11 other Robert Martins in TN with similar birthdate...)
Name: Robert Martin
Age: 6
Estimated Birth Year: abt 1934
Gender: Male
Race: White
Birthplace: Tennessee
Marital Status: Single
Relation to Head of House: Grandson
Home in 1940: Knoxville, Knox, Tennessee
View Map
Street: Cornelia Avenue
Inferred Residence in 1935: Knoxville, Knox, Tennessee
Residence in 1935: Same Place, Knox
Sheet Number: 5A
Neighbors: View others on page
Household Members:
Name Age
Josie Martin 49
Katherine Martin 26 daughter
Francis Martin 16 son
Robert Martin 6 <----------grandson
Annie Shaeffer 82 mother