Owing to a poorly defined sense of self, people with BPD rely on others for their feelings of worth and emotional caretaking. So fearful are they of feeling alone that they may act in desperate ways that quite frequently bring about the very abandonment and rejection they're trying to avoid.
Parentified children learn to take responsibility for themselves and others early on. They tend to fade into the woodwork and let others take center stage. This extends into adulthood - adult children may put others' needs before their own. They may have difficulty accepting care and attention.