D.B.
Sounds miserable all around. It seems like there is a lack of consistency and discipline over several generations. Your daughter, for whatever reason, doesn't make her children feel loved. She'd rather give in to the screaming than make anyone go without, no matter who else that hurts. As her mother, you'd be the best one to judge where this attitude developed. It sounds like everyone deals with conflict by leaving - going to a separate room, moving away, separating, etc. No one seems to have one home they can depend on.
I think it's astounding that a 4 year old recognized you after 9 months and ran away from his mother, and that you immediately took him away from her and into the house to see his grandfather. Do you think this was helpful to your relationship with your daughter?
Be careful with diagnosing things like PTSD. That's a complex series of factors and requires a child psychologist or psychiatrist to really evaluate. However, disruption and not feeling that someone belongs anywhere is definitely cause for distress.
I understand that parenting when you are a grandmother is exhausting. think grandparents trying to parent one grandchild and not others is going to mess up the family dynamic if you life on the same street. I think significant family counseling is in order because these children have all been raised to see that the adults in their lives are there for a while, then leave, then come back. That's incredibly stressful to a child's sense of wellbeing. Appearing to favor one grandchild is just as damaging as your daughter's parenting style, which shows favoritism. I think everyone needs significant counseling to help sort out what's helpful, what will work, what won't, and what sorts of things to say and not say for the children's overall wellbeing. You cannot counsel Lium yourself, or Wyatt, unless and until you have a better understanding of all the issues involved, from family history to the current situation. This has NOTHING to do with how smart anyone is. It has to do with stability - and there is very little of that going on in this situation as you describe it.