First, Gibson was added backwards. The real Samuel Gibson Teter was a great-great-grandson of Samuel Teter and Mary Doddridge, born 1868 Ohio, died 1950 California.
Second, there were a few Teter-Dieter immigrants in the early 1700s living in the colonies from New Jersey to Virginia, and only theories, no proof, of which family Samuel came from. The earliest records I have found show his military service in Maryland during the French and Indian War. There were other Teters in the Maryland militia rolls from that time, but again no proven relationship.
The closest clue to a possible sibling is a George Teter whose military service paralleled Samuel's. This George is believed to have been the husband of Sarah Pearis, settling in Virginia after his marriage, and their descendants went into Kentucky and Missouri.