This is an important question. The child is insecure. The parent's qualities reflect on the children and forms the core adult!. I have come across in my own life and in the lives of someone I know, how the parent's emotions is passed on to the children and subsequently as an adult.
Insecurity stems from the childhood. Parents themselves might have been a victim to their parent's limitations.
"Don't blame others bcoz others have others to blame"- Swami Dayanandaji