Lack of communication skills or lack of compassion?

If you're new here or otherwise unfamiliar with me as a poster, please know that I'm now divorced so I'm not looking for a way to resolve this issue vis-a-vis my ex-husband.  Instead, I'm still trying to process how and why the relationship went south and maybe helping someone else here in the process.

My ex has a different style of communication than me.  His style while we were married was the following:  when he was out of town for days at a time (e.g., at his parents' home, 150 miles away), he did not call, email, or respond to my calls and emails.  This style continues to this day, not surprising now because we're divorced.  But the pattern of what he does remember and communicate about is also consistent.  For example, when my nephew was diagnosed with a very serious form of cancer, while ex and I were still married, ex did not follow up with me to ask how my nephew was doing, even when we were in the car together driving to our daughter's college graduation.  In contrast, when I called ex a few weeks ago to ask him about his ailing father, he did respond and then ask about a plumbing issue in my house (formerly our house), for which he feels some responsibility.  However, he did not ask about my dog, who he knew had been sick and was getting checked out for a possible serious illness (which the dog does indeed have).  

Ex has said to me at least two times over the years that he is unable to form close emotional connections.

So, is the communication problem an outgrowth of not wanting to form close emotional connections or is the inability to form emotional connections an outgrowth of the poor communication style?  And in either case, is the lack of compassion separate or indistinguishable from the communication issues?