The classic MB infidelity formula, in other words. The timing of it was atrocious though-the man was already going through something and it may have looked to others like you were kicking him when he was down (not that I'm saying you were, I'm sure you didn't plan it that way).

I fully understand that if he had been on top of meeting your ENs, the HS boyfriend would not have had an in. Still, this bothers me; maybe because I can identify somewhat with your husband, I also lost my mother and brother a few years apart, and I'm still feeling the loss-they were just about my only remaining blood relatives. It would just about kill me if my wife went off and had an affair while I was trying to deal with these losses.

However, I'm guessing your husband's depression went on for a long time after the deaths in the family, and seemed like it would never end?