Deal Breaker

I recently broke off a short term relationship. Problem is I can't tell him why.
Back in college I had an affair with a married, older professor. It lasted nearly a year. Well the guy I have been dating for a few months invited me to attend a backyard BBQ at his families house. To my shock his dad is the college professor I had the affair with! When we came face to face with his wife standing beside him, we both nearly fainted. I can't tell the guy I fucked his dad!