Trauma makes a child's brain development freeze, damaging the growth process.
Trauma can come from something as "simple" (and less recognized...) as emotional abuse.
Critical thinking, future planning, advanced decision-making are all skills that develop in the portion of the brain that goes on "freeze" in response to trauma.
Recurring trauma = partial and/or delayed development of those necessary adult skills.
If my stepkids' mom was traumatized, which caused her to be a full spectrum narcissist...
Then she emotionally abused, neglected, manipulated, and controlled my stepdaughters...
They will have developed differently than a child growing in a healthy environment.
If you are dealing with manipulated kids or teens, please check out resources that will help you understand them, talk with them, and understand what they've been through. It will be good for your sanity, understanding what in the world is going on over there in the other house.
I wish that I had been given, "Will I Ever Be Good Enough? Healing the Daughters of Narcissistic Mothers" by Dr. Karyl McBride, almost a decade ago. How much it would have helped me understand them, relate to what they are going through and have gone through, and maybe work with them. How much it has helped me understand my husband's struggle with his first marriage, albeit indirectly.
[My favorite finding from this book happens to be that narcissistic mothers of daughters are jealous of fathers, a daughter's good relationship with her father, in marriage and divorce.]
Divorce is a type of trauma for kids, so even if you don't have specific parenting abuse concerns, it may still be worthwhile to look into ways to help kids work through trauma, in general, in order to help them come out the other side with strengthened emotional capabilities and healthy patterns.
My MIL recommended a book I can't wait to get to yet called "Stop Walking On Eggshells: Taking Your Life Back When Someone You Care About Has Borderline Personality Disorder." A friend of mine recommended "The Sociopath Next Door" and made her kids read it. I strongly recommend Divorce Poison for any parent watching their kids be emotionally turned against them.
Find these resources early on, to help you understand your stepkids, their mom, and your husband's experience with his ex. I'm figuring out so much...you know, like 9-10 years in...I would have been a better stepmom if I had read Dr. McBride's book when she first published it in 2009.
But still, it's worth it. One stepdaughter, in the midst of the beginnings of teenaged worlds, has recently figured out quite a bit about her life, her mom, and her reality. She was hurting, while also becoming strong. I wanted to help her, because she was coming to me to talk about her struggles with her mom and defining who she is. I then desperately searched for resources to help her, and I will continue to help her deal with her new, enlightened, but somewhat painful world.
My other stepdaughter needs some help with the same, but doesn't realize it yet. She is just starting a pursuit of independence, but doesn't realize the struggles she has ahead of her. We need to be very smart, and purposeful, in order to help her. It will be a longer road, which hopefully we're already halfway down.
We were brought into our stepkids' lives for a purpose. You may one day have a purpose and be the mom they never had. Or if not that, help them to become more emotionally confident, stronger women, smarter men, caring humans. It is not all your burden to bare, but you do have the opportunity to make a difference in this world by strengthening your stepkids- if they give you the chance.