I believe at least one of my step-brothers has some fetal alcohol effects from his birth mother, who was an alcoholic.
A few years ago, he wanted me to show him how to do long division. He just could not grasp it. Most middle elementary students can do it.
He spent three years in sixth grade, and then dropped out. He was such a difficult child, teen, and adult. He did mellow out in his mid-to-late thirties, I think. He is a better grandfather than he was a father. He is also a wiz with carpentry, plumbing, wiring, auto repair, boat repair, handyman jobs, etc.
He is doing better than any of his other siblings from his bio-mom. Two are deceased, and two are much like your ex-daughter-in-law.
I love him so much, but can only be around him for short periods of time. He drinks too much and sometimes is irrational and gets angry, though never directs his anger at anyone, or is in any way threatening.
He is also someone who would give his shirt off his back to anyone. He does so much for so many in his community, helping elderly and disabled with his home and car repair skills for free. It makes me ashamed in comparison.
He often talks of dying.
People can sometimes take advantage of him (I feel).
He loves to talk about his escapades as a pre-teen/teen/young adult, which he clearly sees as the best time of his life. He wants to discuss endlessly (our) highly dysfunctional family life from our childhood, and really doesn't see it as dysfunctional. He loves to tell all his stories to my hubby, which I hate. I don't like reliving any of it, and he can't see how terrible it sounds. I am embarrassed by it. Hubby had a Leave-It-To-Beaver childhood, for the most part (normal, anyway). I try to explain my feelings to my brother, but he persists.
He also sees everything in the past from a point of view that most of our difficult adults have--that he was always a victim and everyone did him wrong. I think he really believes his version of things, which often bears no resemblance to reality.
These relationships are so difficult.
However, my brother has made a life for himself, and I am thankful for that.