Okay, this is a question for my SIL.
Background: My SIL has 5 kids - 13 year old girl, 8 year old boy/girl twins, 5 year old boy, and a newborn girl. The 3 oldest kids are from her first "relationship" (Engaged but never married). The youngest two are from her current marriage. The kids live with my SIL and her husband (Who raises/treats them like his own and loves them just as much as his own), and do every other weekend with their father. I don't know the full story, but their father sounds like a complete ****.
Situation: Her 8 year old son was potty trained. No accidents what-so-ever for a year and a half. Then one weekend he stayed at his father's house. When he got back, he was no longer potty trained. My SIL says that it wouldn't surprise her if her ex had somehow convinced her son to do this. I guess he has convinced them to do other things before (Like saying hateful things to their mom, fighting with each other to stress mommy out, etc). I found this out because I've been watching the kids this week (The 3 oldest kids were at their dad's Monday/Tuesday and Wednesday my SIL took off work to take them all to a Dr appointment, so this was the first day that the 8 year old was with me). Towards the end of the day, I noticed that something stunk. It wasn't my two year old and it wasn't the newborn. I asked the 5 year old if he had an accident, and he said no. Then the 13 year old told me that sometimes the 8 year old boy had accidents. So I asked him and sure enough he admitted that he had pooped his pants. Why? Because he was too busy playing. Now he had used the bathroom several times during the day, so it's not like he doesn't know HOW to use the bathroom... He just chose not to. I made him clean up the mess on the floor (Some of the poop had fallen out of his underwear and onto the carpet in my son's bedroom) and clean his underwear and himself (There wasn't any extra underwear or pants for him in the bag my SIL packed (She forgot because his grandma (The person who usually watches him) has clothes for him at her house).
So when my SIL came to pick up the kids I told her about it. She has said that it has been going on for over a year now. They have taken him to his doctor, who said there was nothing physically wrong. They have tried punishments, taking away favorite things (For example: He is not allowed to play the Wii (Which he loves) until it stops - He doesn't care), and rewards for when he does use the potty. They have had people that he respects try to talk to him. They have asked him why is does it and come up with a solution to every problem (Example: Why didn't you get out of bed to use the bathroom last night? I woke up but was afraid of the dark. Okay, here is a night light.). When he does it at their house, he has to clean up whatever mess on the floor, scrub his underwear out in the bathtub, and then clean the bathtub. They have tried everything that they can think of and he just doesn't seem to care. He does it everywhere. At home, at his dad's, at his relative's houses, at friend's houses, at school... Everywhere. They just can not figure out a way to solve this problem.
I offered to post a question about it on here and see what solutions you ladies come up with. Maybe you can think of something that they haven't thought of?
P.S After his "accident" today, I talked to him and we agreed on what punishment would happen tomorrow if he had another "accident" at my house. No more ipad for him. Hopefully he won't do it again, but we'll have to see.