They would not have had their other kids taken.
They were parents who got their risk assessment badly wrong and the highest price was paid.
Do you really think they were an ongoing risk to their kids? Or that they would have gone on hol the next year and done the same thing?
Or that the traumatised twins would have benefitted form MORE trauma in being wrenched from their parents and put with foster carers?
Are you an experienced social worker who could vouch for the fact that children would be removed under those circumstances? And if wc?
It seems to me that the bar is vey very low (or high, if you like) for the removal of children and there are many children who have been left in the care of violent / addicted / non engaged parents.