Just a thought. I have 3. 2 boys and a girl. The first time was my oldest son. He was around 8, and dad had just come from a convention and was oc. We thought our son was at friends house, as we're getting into the middle stages, we heard something, babyboy walked right in on us. Hubby talked to him later.
The second time was lil man (just turned 12). We had been on him about walking in without knocking. It was midnight, so he was asleep. Unfortunately he had a nitemare, so walked right in. Hubby got so mad. I calmed him down. So he talked to lil one. Daughter never walked in on us.
Talk about a letdown for hubby.