Often fathers who do not live with their children feel guilty and try everything to keep on the 'good' side of their children by showering them with gifts and not challenging bad behaviour. My advice is to sit your children down and have a 'grown up' discussion with them both, your son is old enough to understand where you are coming from and to acknowledge that if he does something wrong he will have to deal with the consequences of it. Ask him to think about what he would do if he were in your situation. I think it would also help if you tried to talk to your ex husband and explain that you feel your sons behaviour is beginning to worry you and you need his help in tackling it. Don't make it sound as if it is all his fault but try to agree some boundaries for your son and ask that your ex sticks by them too. Good luck