Here is the relevant 1940 census (some surnames were misspelled in transcription) with both Roy's father Donald and grandfather Frank:
Name: Frank S Glane
Event Type: Census
Event Date: 1940
Event Place: Union Township, Union, South Carolina, United States
Gender: Male
Age: 38
Marital Status: Married
Race (Original): White
Race: White
Relationship to Head of Household (Original): Head
Relationship to Head of Household: Head
Birthplace: North Carolina
Birth Year (Estimated): 1902
Last Place of Residence: Same House
Household Role Gender Age Birthplace
Frank S Glane Head M 38 North Carolina
Lenora H Glane Wife F 37 South Carolina
Francis H Glane Son M 16 South Carolina
Gene D Glass Son M 12 South Carolina
Donald E Glass Son M 5 South Carolina
https://familysearch.org/pal:/MM9.1.1/K46K-L3B