Unrelated Family
Here’s the thing about DNA testing, they’ll take a sample of blood, skin, hair, or other tissue from the mother, child, and father to determine what genetic markers—special characteristics—the child shares with the mother and would-be father.
These tests are also pretty accurate when performed correctly, and the likelihood of error is limited. It’s likely that this man’s suspicion is correct, and he was switched at birth. Yet it’s understandable that he has no idea how to broach the topic with his folks.