I did find this family in Patrick co., VA in 1850 so your theory may be correct. It seems that the Goins were numerous on both sides of the VA-NC border in that area. I noticed that there was an Allen Goin living quite near to Henry and Zelphia. He is close in age to Zelphia, so he could be a brother.
Two researcher online posted that Zelphia was the daughter of James Stephen or Steve Goin, a son of Shadrack Goin. I did find a will for this James, but it only lists daughter Prudence and Betsy and Nancy as daughters.
I would find a local Latter Day Saints Family History Center and order the marriage records for Patrick Co., VA.