Second Marriages and children that are problems what would you do?

Sorry so long!
Because there are a lot of divorces these days there are often new family units being built by the new partners?

Let’s say you have a child from your first marriage, and then you have another one or two from your 2nd Marriage. But let’s say your first child “John” has behavioural issues. Like ADHD, also tends to lie and steal. He has what you would term “out of control behaviour”:

Wife no. 2 puts her foot down and says “Get rid of him send him back to his mother, or boarding school or whatever: The marriage breaks up, and a new wife moves in knowing by now there are 3 children. She also finds out that the first kid John is a handful. All the wives are very young. (Age range 18 – 23). She also puts her foot down and makes the dad “choose” between her and the kid John. Meaning divorce.
The dad shoves John into boarding school and so it goes on. Dad is an absent father due to much travelling. By now John who has always had issues gets worse. Takes drugs, lies, steals, is basically a dead loss. But is also a lost human being. The father marries again, to a person the same age as John. John having had bad experiences with wives takes an instant dislike to the new wife, as he had all the others, as they had disliked him for their reasons. The new wife has three children quickly they are all small babies, now that John is an adult although she tried; she bans John from family occasions. John feels like he has no family or at least had one but is ousted. He confines in me this is how he feels. He seems lost and aimless even as though he is an adult.
The question. If you are a person marrying another person who has children, is this not part of the package for better or worse? Why fluff your feathers and start demanding separation from the child even when he was 10 when you knew beforehand this child was an issue. Did everyone expect the child to disintegrate? Or do they have rights and good reason to expect this child now an adult to disappear? If John has started to change can he be given a second chance? Whose home is his father’s home, is it the new wife’s or the dads home, or is it everyone’s home including Johns?