Thanks, shortfiction.
I'm sure that Ennis at some point in the future probably will go back and visit the Twists.
And this may seem a bit wierd to you guys but in my personal opinion, when Mrs. Twist was very warm, welcoming, and soft towards Ennis, that 'probably' showed Ennis that he was NOT being rejected by someone. This maybe my own mind track thinking on my point of view of it but I have a feeling that Ennis realized that he was actually being WELCOMED into. Not that I'm saying that Jack, his daughter, nor Cassie weren't doing that. It's just he really didn't know how to accept their invitations because of his severe phobia that would prove to be his undoing.
After Jack's passing and the soft mannerisms toward him from Mrs. Twist, Ennis now accepted someone's sweet gesture toward him without rebuffing it. He now knew that not everyone can be so cold(i.e. his own father and Jack's father, among people).
Jack's mother showed him some comfort along with some maternal-like feelings toward him when he went to visit them. And he hadn't felt that way ever since his own mother had passed. It was really nice that the love's of his life mother was so polite and caring towards him during his mourning of her beloved son. And he took in that welcomage and started to change his views on himself and how he should be more willing to accept those who express their love for him. Even though he was still in pain after Jack's death, he looked as if he'd learned a good lesson and started to live by it.
Especially at the end of the movie with Alma Jr. It looks as if he was taking his steps to accepting himself and others as they shared their concern and care towards him.
But, hey, that's what I got out of it. It can be anybody's interpretation to guess how the connection with Ennis and Jack's mother was.