J.C.
This is a complicated situation but I will try and do my best in a short email. I was a single parent for 7 years and have 2 sons (now grown) so I can relate. At about 12 years old or maybe a little earlier, the Calif courts allow children to make their own decisions about visitation and who they want to live with. There are pluses and minuses to this.
I would suggest you have a heart to heart with your 13 yr old and ask him what he really wants. Have him make up a list of the pros and cons of reducing his visit time with his Dad.Get permission from him for you to give him your opinion but act as a consultant rather than "This is what you have to do." I would still encourage him to have some contact with the Dad. Both for his brothers sake and his own. You never know, there is always the possibility for change.
Once the two of you have a plan, make a date to discuss this with the Dad. This will not be easy for anyone, but if you don't involve your son and give him the opportunity to make decisions in his own life, he will continue to feel powerless which is what he feels now.
If would like more help privately, you can go to my website: www.janadaclark.com and contact me as I do work with families in similar situations.
Sincerely,
J. Clark, MA
Parent Educator and Wellness Coach