AFTER READING YOUR SO WHAT HAPPENED:
Learning that you aren't the mother of the 13 year old helps to understand his behavior. He's suffering from the feeling of abandonment from his birth mother, not matter how good you and his father have been. Still this no excuse for delinquent and disrespectful behavior.
If you or dad are at home with the boys, it looks like your just going to have to get tougher and be consistent. Take door off their bedrooms and the dresser out , they can hide things in there. Show them that if they want privacy and their material items returned, they will have to earn each thing one by one.
D.,
It sounds like your family has a lot of material possessions and your children are stealing from home. Are they stealing from outside the home?
Since your boys don't obey, respect or listen to you, dad or the therapist, it may time for another solution. I would suggest contacting your local police department and see if there is something like a "Scared Straight" program in your area. I would also see if the juvenile department could recommend a different therapist.
There are also private schools that specialize in helping troubled children. Here is one url: <adolescentcrisisteam.com>
These programs are very expensive so if this is not an option it's really time to put the hammer down at home. They should not be left alone at any time. If they have stolen things outside the home contact the police and juvenile authorities.
Get to the bottom of the telephone SIM card and contact the parents of the other child assisting your boys in stealing.
You might also consider clearing your room out to the point that it is not necessary to lock your door. In order to improve the morals and standards of your children, you and dad may need to evaluate your own standards.
Place the only tv and computer in your in a family area. You can control access to both tv and computer with pass codes. Have family time for tv and at least eat dinner together during the week. More time together on the weekend.
Your boys are in trouble and it appears that all concerned will have to make some sacrifices and lifestyle changes in order to bring them under control. They need to be pretty much grounded with no outside activities except for school until the can prove they can be trusted.
Blessings.....