It sounds like you have done all you can. If you leave the door open, maybe someday he will have a change of heart. That happened with a family member of mine. Once the mourning period was over, in this case about 8 months, they came back and our relationship was stronger than it ever was. They described the same feeling, that the other person had died, and that they are now getting to know this new "long lost family member" they never knew before.
But everyone is different. Another family member and I haven't talked in years, and I doubt we ever will. Don't try too hard, the decision is with him, and no amount of well-wishing on your part will change his mind if he's not open to it.