Are you a parent? Do you understand the challenges of parenting that includes the fact that "controlling" your child is ultimately impossible?
Yes, you can be attentive and engaged, ensure they're mentored and guided, are given discipline and instruction, etc. But they're still autonomous units that are going to do what the fuck they want to do.
Of course there are cases of abuse that can damage a child but that should not be a base assumption in this case (his other children appear to be fine).
"Hungry Ghosts" (or "Scattered Minds") by Gabor Maté is a very thought provoking book and quite relevant to the subject.
We are not well-served by treating addiction as simply a matter of will-power and "character".
This isn't to say that we don't all bear responsibility for our conduct as best we can, but sometimes it's way more than that. It's like accusing a schizophrenic of not trying hard enough to "be normal".