Descendants of James Rampley (1803-1884) insisted he was the only member of his family who came west to Illinois from Ohio. "No other family members came here" was what I was told.
James bought his first Illinois farm from a first cousin. His sons served in a Civil War unit with a near neighbor whose grandmother was a Rampley and another set of cousins lived about ten miles away. While the cousins ten miles away might not have been on James' radar, he clearly knew about the others. The "no other family members" was not correct.
What the teller of the story might have meant was that no one in James' immediate family of siblings settled near him. That was true. Always look for relatives in the new area where your ancestor settled, despite what the relatives today may insist is true.