There is a husband and a wife that, over their marriage, have eight kids.
One day the husband notices that their sixth kid, Billy, looks very different from the other seven.
The husband goes to his wife and asks her, “Honey, I noticed that Billy looks different from the other children, did you have an affair?”
The wife starts to break down into tears and nods her head.
The husband, heartbroken, quietly asks his wife, “So who is Billy’s father?”
“You.”