Unfortunately this is not always the case. All too often some unresolved issue in the parent's or sibling's own past influences how they treat the unsuspecting child. The children hope that by improving themselves they can improve their family. Such a hope is doomed to failure and the child is left feeling inadequate. We are products, but we are not prisoners, of our past.
Adults take responsibility for their lives.
After childhood, we can choose to love ourselves, to see ourselves, no longer as victims, but as loveable and capable people. Love, including self-love, is a choice. We can learn to love ourselves as God does, because of who we are, not because of what we do. Those of us coming from troubled families can learn to stop blaming ourselves. Our parent's negative behavior is that of the hurt or angry little child within the parent and not our fault.