Be open to the possibility that more members of a family immigrated than you think. Family tradition was that an ancestral couple married in Switzerland and then migrated to the United States in the early 1850s where others of his family had settled as adults. Seemed like a very reasonable story.
Turns out that the wife immigrated as a child with her parents and that her future husband immigrated as an adult from a nearby village with members of his own family. She was not the only one from her family to immigrate as the family tradition seemed to suggest.