I don't believe that Garrett and Barnabas are the same person. Yes, I believe Barnabas is Felix's dad. Fee lix had a daughter named Rebecca C. Vanzant. She married John Wesley Rose. One of their children Sarah C. Rose married John J. McCoy. One of their sons was William Thomas McCoy. He married Talitha Rebecca Lane. One of their sons was J.T. McCoy. He married Ethel Mae Smith. I am one out of seven children from that union. I found a Barnabas on 1793 census of Straban Township York County Pa. I also found a Peter Vanzant and Brandas Vanzant(possibly Barnabas) on the 1784 and 1785 census of Straban Township of York County PA. I am researching to see if this Barnabas might have fought in PA and was granted land in Surry County NC.
To answer your question of other children of the Vanzants.
The Vanzant, the Rose, and the McCoy families left NC to travel together to Scott County VA and settled in the Powell District. The Vanzant, the Rose, and the McCoy families then moved to Texas. A brother, Alexander Rose stopped and settled in Scott County AR and then later moved further east in AR. This how far I have gotten thus far. You might look for some of the relatives in NC, VA, TN, AR, TX. I say TN because the Lane's also lived in the Powell Distraict of Scott County VA so some of the Lane's on the wagon train to Texas stopped and settled in TN along with some of the Lane's who had never left TN.