IMO where one child grows up to really disrupt the home, and other children that are fine, it is usually down to the parents.
By that I mean, the parents are usually gentle, too tolerant and too appeasing.
The child was probably a stubborn, headstrong toddler that needed a very different type of parenting to the others.
Unfortunately the parents weren't equipped with the skills and strength of personality to manage the challenging child.
It isn't easy to parent strong willed toddlers.
It isn't easy to be very firm and consistent.
It can cause terrible upset in a marriage if parents are not on the same page.
The child goes from toddler to pre teen, always being managed, accommodated , pleaded with.
Now the above is the extreme end of what happens and I have never heard of it.
However, I do know where there can be one child in 3 or 4, that needed a different type of parenting to their siblings.
I feel very sorry for the parents involved.
Busy lives, working FT, juggling so much, it can be very difficult to find the energy day in day out to stay firm.
Things then slowly escalate....a bit like the boiling frog analogy....and you have an utterly out of control situation.
I very strongly believe no one family member can be allowed to cause havoc in a family like above.
So yes, post 18, they should be asked to leave.
Siblings have every right to feel huge resentment towards their parents for allowing this to happen.