Need ADDers opinion on why the communication issue

I really wish some of those with ADD could help me to maybe understand this communication issue.  My husband always hated it when I would talk about how I felt.  He would always say, "I don't want to argue".  Even when our older son would express his feeling, sometimes crying, sometimes sobbing, due to his ADD/depression my husband would sit there stone faced and say not one word.  Once when our teenage daughter was going through the 'rude' stage, my husband actually didn't say a word to her for a month.  My husband once told me about a couple he knew who would 'talk it out' when they were having marriage problems.  My husband responded with, "I could never do that".  Well, now my ex has been gone for 4 years but still will not have any type of emotional conversation with our son or really ask him about his job, etc.  I will email my husband once in awhile and tell him about our son when our son is so upset, threatening suicide, crying, depressed etc, etc, and I ask him to please be more involved and that i cannot continue to deal with this alone.  After almost 4 years my husband will only answer back with 3 to 5 words but he never gets more involved or says much else in the email.  If it was a case of him just blowing us off after he finally left his marriage and is now living the single life in a way I could understand it but this is how he was when he lived in the house for years.  Please tell me what is going on possibly in his brain to behave like this.  It is the most frustrating and painful thing.  What do you think he is feeling? Both his kids have just about written him off.