Trauma Bond

Our therapists thinks that there is a strong possibility that our foster kids have a trauma bond instead of a normal sibling bond. She is concerned that they need to be separated do to aggression from the oldest toward the youngest. She wants to really be sure before separating them, but she thinks that may be the best/only way for both of them to heal. The oldest also has moderate attachment issues but is making some progress in that aspect. Has anyone had experience with this type of bond and did they have to separate the siblings? We are really hoping it won't come to that but we are not a therapeutic home and that may be what he needs.