Not necessarily. If they got involved because of another child, they are hard to get rid of. She may have been young, with no parenting skills and the inability to care for a child. The fact that she didn't seem to have a stable home gave them pause.
I know of some pretty awful living circumstances for children that even when the ministry is involved the children are not taken away from the parent even if that parent is in all kinds of trouble.
One case I know of is a mother who lives with the boyfriend (father of the child) and his family. They are all heavy drug users and live a life of crime and many horrible scenarios, they are well known to police. There is even a no-contact order between the mother and father of the child, but that does not stop them. The young child who is now 3 years old was finally surrendered to Child Services by the mother. The family who was trying to save the child from the living circumstances had to push and follow-up and demand and still nothing was able to be done. It was only once the mother surrendered her child.