When my husband and I separated I took our 3 eldest children to therapy..My sons were 20 and 18 and my daughter was 16..I asked them to please go to discuss whatever they wanted..I did not go in with them..My 18yr.old was very angry, and the T felt that therapy would help him with that..so I brought him for several sessions, but he would not talk there..really didnt share anything, so he discontinued therapy..my hope is that someday he will return..maybe you can encourage your son to go for a "couple" of sessions, and with the premise that it is for him to be able to discuss how the divorce is affecting him, or just talk about anything he wants..hoping and trusting that this will work out for you and your son...