Need a solution

My take on this:
While stress may be partly responsible, this is HUGELY a personality related thing. Thats his personality, and while it is a very difficult one to live with, thats how he is wired (more solo, more lonely / introvert type). "I wont bother you, you wont bother me, we are like roommates, except in issues related to kids where I will be generally responsible" types.