Welcome to G2G forum, Jason.
If the information that I found is accurate, the names of your second great grandparets are Adam and Josephine Grubb, your third great grandparents were William and Sarah Grubb.
Your grandparents, Sidney Bryant and Barbara Lee, got married on 1951:
Name: Sidney Bryant Grubb
Event Type: Marriage
Event Date: 21 Jul 1951
Event Place: , Tazewell, Virginia, United States
Birth Year (Estimated): 1929
Father's Name: Sidney Bryant Grubb
Mother's Name: Lena Isom
Spouse's Name: Barbara Lee Davidson
Spouse's Birth Year (Estimated): 1934
Spouse's Father's Name: Rassie Davidson
Spouse's Mother's Name: Florence Walker
Certificate Number: 21228
Digital Folder Number: 101169414
Image Number: 00129
Citing this Record
"Virginia, Marriage Certificates, 1936-1988," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:QV1M-L3PJ : 10 January 2019), Florence Walker in entry for Sidney Bryant Grubb and Barbara Lee Davidson, 21 Jul 1951; from "Virginia, Marriage Records, 1700-1850," database and images, Ancestry (http://www.ancestry.com : 2012); citing , Tazewell, Virginia, United States, certificate 21228, Virginia Department of Health, Richmond.
Your great grandparents, Sidney and Lena, got married on 1927. The following link is to the document, the marriage license is in the right hand side page (Page 129), you can move within the image using the arrow keys in your keyboard:
http://www.wvculture.org/vrr/va_view2.aspx?FilmNumber=806456&ImageNumber=433
According to this document, Sidney was 21, and his parents were Adam and Josie Grubb.
Adam and Josephine in the 1920 Census, Sidney was 13:
Household Role Sex Age Birthplace
Adam W Grubb Head M 34 Virginia
Josephine V Grubb Wife F 31 Virginia
Sidney B Grubb Son M 13 Virginia
Bertie E Grubb Daughter F 10 Virginia
Homer Lee Grubb Son M 8 Virginia
Luther Ray Grubb Son M 5 Virginia
Citing this Record:
"United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MJJK-H7L : accessed 25 April 2019), Adam W Grubb, Speedwell, Wythe, Virginia, United States; citing ED 191, sheet 16A, line 14, family 274, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, 1992), roll 1919; FHL microfilm 1,821,919.
Adam and Josephine in the 1910 Census, Sidney was 3:
Household Role Sex Age Birthplace
Adam W Grubb Head M 25 Virginia
Josie V Grubb Wife F 21 Virginia
Sydney B Grubb Son M 3 Virginia
Bertie Grubb Daughter F 0 Virginia
Citing this Record:
"United States Census, 1910," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MPGX-878 : accessed 25 April 2019), Adam W Grubb, Honley, Wythe, Virginia, United States; citing enumeration district (ED) ED 146, sheet 1A, family 9, NARA microfilm publication T624 (Washington D.C.: National Archives and Records Administration, 1982), roll 1652; FHL microfilm 1,375,665.
Adam and Josephine got married on 1906. The parents of Adam were William and Sarah Grubb:
Name: Adam W. Grubb
Birth Date: 1885
Birthplace: Wythe Co., Va
Age: 21
Spouse's Name: Josie V. Stroup
Spouse's Birth Date: 1889
Spouse's Birthplace: Wythe Co., Va
Spouse's Age: 17
Event Date: 18 Jan 1906
Event Place: Wythe Co., Virginia
Father's Name: Wm. Grubb
Mother's Name: Sarah Grubb
Spouse's Father's Name: James Stroup
Spouse's Mother's Name: Lennie Stroup
Indexing Project (Batch) Number: M01400-9
System Origin: Virginia-EASy
GS Film number: 34255
Reference ID: P101 L7
Citing this Record:
"Virginia Marriages, 1785-1940," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:XRSC-RNX : 11 February 2018), Adam W. Grubb and Josie V. Stroup, 18 Jan 1906; citing Wythe Co., Virginia, reference P101 L7; FHL microfilm 34,255.
