Parentification can occur when one or both parents have mental health issues and it seems to be common in narcissistic families where the family is structured around getting the needs of parents met, rather than providing a healthy environment where children are nurtured.
or when parents are deadbeats, drug addicts, alcoholics, are general selfish losers who outright neglect their kids instead of owning up to the responsibility of being their parent.
I had no childhood, or young adulthood to enjoy. I can't recall a single happy memory growing up. It was always miserable; fraught with chaos, frustration, and worry coupled with filth and poverty.
In my case, it is a co-mingling of sick narcissistic dynamics (mother) and a father who was basically a negligent loser. He bailed to go have a 'real' family with some side-action piece of trash named Barbara. He left his kids behind to fend for themselves. And mommy dearest was a lazy, manipulative piece of work.
From the time I was barely 13, I was officiated as one of the 'parents,' left to take care of myself as well as my younger siblings and my mother after my father left. It only got worse after my older sister left home. Imagine having the needs of others as well as costly bills and responsibilities foisted onto you in your teens? By the time I was 20, I was paying the mortgage and most of the household expenses because our mother 'faked' being too sick to work and insisted her kids cover the costs of basically everything. It wasn't until I was a working teen that we had regular food in the house (food I was paying for). The financial abuse was unreal (as she would create expensive costly messes I was put in the forced position to clean up). We were brainwashed young to believe you take care of family no matter what, so that is what we did. Even when the abuse increasingly worsened. She wanted to make sure I was suffering financially so I couldn't leave like my sister and my dad, while telling me everyday how horrible they were and how much like them I was. And if I left, I too would be a monster abandoning her like they did. Christ, when I finally went no contact and left for good, it was like a prison break.
A young adulthood of being a surrogate parent to a household of people who treat you like a living wallet, after a super-shitty childhood of poverty and neglect makes me somewhat bitter as an older adult. I have a little chip on my shoulder when I hear about people who had loving, supportive parents and gush about how great their life is - how easy things have been for them because their parents built them up, helped them into college, paid for college, helped them get a car, a home. I started way behind the 8-ball compared to those people and had to work against the current for everything I have. And those super lucky people who had awesome parents dare to victim-shame me when I say I have nothing to do with mine.
I do sometimes think where I'd be had my parents not been the loser self-important a**holes they were. So I just live my life trying not to be a loser self-important asshole like them and try to still do some good, to be kind, even when things are hard.