Dr. Jacqueline B. Sallade offers ideas for maintaining your mental health.
A child doesn't have to be of a certain age to end up in the position of a mini-adult. Just a little four-year old can act grown-up to compensate for a handicapped or particularly immature parent or sibling. He's the little hero in the family, trying to hold it together in his own brave, stoic way. He's polite, responsible, cooperative and calm. He stifles and shuts off his poor little emotions. More typical is the older elementary school child with an absent or unpredictable parent, who takes care of the other parent, becoming a helpmate and companion. Whether or not she conflicts with the dysfunctional parent, she learns to cope with life by living around that parent's caprices. In the most horrible cases, I've seen this child become oversexualized and even used sexually, too. Hard to comprehend but it happens.
Then, there's the teen who's able to rebel a little, make a few mistakes, learn from experience and take it home to show her new maturity by understanding more than one or two of the parents she finds there. She takes care of the younger children, sets her own limits and excuses or puts up with the parent(s) without overidentifying with them, just biding time until she can spring free and have independence. She worries about the situation, especially if there are innocent siblings. Her hypermaturity may come back to haunt her with undue stress later and a need for relief through unhealthy behavior, or she may learn to play in a constructive and healthy way. I've seen both--the college kid who drinks now that she's free or the one who loves sports and music and does well in school and life, for example.
While the child who acts like an adult is admired by amily, teachers and peers, it's not a good state of being. The real danger of parentification is that it is a reaction to insecurity, which leaves residues of pain. What kind of dependence on a partner in the future to compensate for that void, what kind of skills developed to grow out of the emptiness and heaviness of it all, really depends on the kid's other contacts and opportunities, her personality overall, intelligence and a whole variety of random factors, even luck.
The best case scenario is exposure to someone, a therapist, grandparent, activity leader, religious type or friend who can offer protection, insight, and love and allow the child to own what it is to be a child, the true dependency, loss, aloneness and wonder, while helping the child use the grown-upness appropriately without needing to be a hero, little professor, or caretaker before his time.