An earlier version of this article incorrectly described the family of Bob Hutchinson, who discovered relatives he did not know of following a DNA test. He has just one sibling, not two, and his mother had just one sibling, not two. The article also incorrectly described the person who began investigating the family’s history. It was Mr. Hutchinson’s sister-in-law, not his sister. In addition, the article misstated the results of the test. He was found to be one-eighth African American, not one-quarter, and to have some Swedish and Italian heritage, not none.