My son's (5) father watched porn next to him in bed.

My ex has our kids( 5m & 4f) for overnights every other weekend. My kids are both still really into cuddling. I know at my house, my kids will go to sleep in their own rooms, then climb into bed with me every morning for the last Couple hours of sleep. I think at their dads house, my understanding is that he cuddles them to sleep every night in their beds, then they all move to his bed later anyway.This morning my son asked if he could tell me a secret. He was worried about getting in trouble but I assured him it was fine. He told me that last time he was at his dad's, during their bedtime cuddle, their dad was watching what was clearly described as a pornographic movie. I don't know if he thought they were asleep or what. He said that he let his sister see. I don't know if that means intentionally or not. We talked about it some more, Ankit what he saw, and I reassured him he would never get in trouble from me or his dad for telling me. I asked if he had any questions and or if there was anything else. I didn't accuse or pry or get mad (outwardly, anyway. Inside I am pretty fucking mad)I have no idea what the hell I'm supposed to do with this information. I'm reasonably sure he didn't mean for them to see it, but what the hell?What do you do in a situation like this? We are going through a custody dispute at the moment, this is not the first incident of inappropriate things they have watched at his home. Im just grossed out at the thought of this happening.Tldr; ex watched porn in bed next to children. What do I do? via /r/Parenting http://bit.ly/2ETtfBv