Is this Complex Trauma or just my wierd family?
Complex typically means that the abuse started young and continued over a long period of time, there was more than one perpetrator, there was more than one type of neglect or abuse: physical, sexual, emotional, psychological, spiritual; or some combination of those things. Other types of complex trauma would include torture, living in a war zone, living in a long-term abusive primary relationship, having multiple hospitalizations or surgeries, and other things like that.
The question about how "bad" it is lies in the details, the age of onset and the length of time it occurred, amongst other things. There are many factors in your family that add to the complexity. Often in this situation, the siblings become part of the pattern in joining the more "powerful" or scary parent in the treatment of the "bad" child. In many abusive families the siblings become a source of support for each other but in those where there is a "favorite", for favors or scapegoating, it pits the siblings against each other. When there is a narcissistic parent(s), or a parent with another personality disorder all of the children are being abused or neglected in some ways, it just does not always look that way. The scapegoat then becomes the object for all of the feelings about the abuse that is happening to everyone so not only is there the primary abuse but there is secondary abuse from others who are in the system. In a way, the siblings deflect their negative feelings about themselves onto the bad child so that kid then is the "carrier" for all of the low self worth and self-hatred in the family. That is also likely what was in part happening with your mother. I am assuming that she had a rough childhood and that all of her self-hatred got centered on and, in effect, transferred to you. Typically, the child either is very much like the parent or very much like the parent's primary abuser, but of course, that is not always the case.
So, was it "bad"? I have no doubt that the impact on you and other people in this situation is profound and extensive. When these things happen when we are very young, all of our developmental tasks occur within and are impacted by that trauma. I think of this sometimes as having the wiring all messed up. The lights turn on and things run in ways that look fine most of the time from the outside. However, because the wiring is crossed and spliced and rerouted so many ways, things get activated that cause chain reactions or old reactions in situations where they no longer fit. Because the wiring gets laid down over all of childhood, stuff that happens later gets interpreted in light of that scaffolding (sorry, I just switched metaphors)
Most people from abusive families have times where what happened to them seems like "no big deal" or "make believe" which just serves to support the original wiring as it was laid down. An implicit, and often explicit message in abusive families is that the kid who is the main target is the "crazy" one or a "liar" or other things that support this notion that what you remember is not really what was happening. There is also often a strong and persistent message to never talk about what is going on so when you are in therapy and uncovering the layers and talking, that part of the wiring gets kicked in, “this must be make believe or not that bad” or some other thing that serves the abusive system. I usually think of it as "family loyalty" that is misplaced and unearned yet still very strongly activated at some points.
What I know from working with you in the context of working with each of your children for a time is that you have done an amazing job as a mother in giving your children the love and support that they need. You did not always have the information and support that you needed so that made it all the more difficult. Your son's wiring also has impacted your other kids greatly, which I see in so many families with ASDs. In addition, you have your husband’s family history and personality that has also contributed to that mix. You have great kids. A big part of that is the ways that you love them. To have done as much with and for your children as you have with what you came from speaks to your strength and resiliency as a human being. I also see that you have worked enormously hard to keep what happened to you separate from your kids and I think that as you continue to heal, it won't be such a struggle.
I think that you are very brave for staying on this path of healing. I believe that on a spiritual level, when we heal from abuse, we also heal some of the abuse in the world that others have not had the opportunity to heal from.