One out of Eight

[Eropagnis]

A man and his wife were celebrating their 50th wedding anniversary. The wife says to her husband, "For our anniversary this year, you can ask me one question, any question you want to. I will answer it truthfully."

The husband replies, "Okay, this has been bothering me for a long time, but I haven't had the courage to ask before...but I have noticed that all of our eight children look similar to one another except one. I can't figure out how he got to look so different. Did he have a different father than the rest?"

The wife stops. She is unable to look her husband in the eyes. Slowly she replies, "Yes.... Yes he did have a different father." Her husband was taken aback. "Oh! Okay...I must know. Please tell me. Who was that child's father?" Again she cannot look her husband in the eyes.
She is very distressed, and after a long silence she slowly said, "YOU."