apathetic 7 yr old deficating in pants

My oldest son just turned 13 and is finally overcoming this issue. His father and I divorced when he was 6 years old and I've always felt his soiling himself was a control issue. His bowels have been the only thing in his life he can control. I think that if there are no medical problems then this is one area we parents just need to say, "Bummer!" and walk away. It is so hard not to sweep in and try to "fix" everything! Or to share your feelings by saying "I'm sorry.....etc." But don't fix and don't make it about your feelings!! Show them step by step what to do including bathing and washing clothes then let him be in charge from that point on. Good luck!