When I was a teenager, one of my friends had a brother who beat her up. At the time, I didn’t understand what that meant and couldn’t reconcile it with what I thought I knew about sibling relationships. To me, the fact that he “beat her up” meant that they got into fights sometimes. And, for me, then, fights were fair and equal matches that both people signed up for.
I remember I mentioned it/them to my parents once, and my dad even remarked with a shake of his head on it. “Isn’t that the boy who beats up his sister?” he asked. And I corrected him. “No,” I said. “They get into fights sometimes.”
I was young and had a limited understanding of the world. However, I knew about intimate partner violence and child abuse by parents/guardians because of soap operas and books. I had no clue that sibling abuse was a thing. I thought that siblings could fight or maybe get on each other’s nerves or participate in schemes and manipulation (okay, yes, this is all stuff I read in Sweet Valley High), but not once did I understand that domestic violence could occur between siblings.