Unfortunately, self-defense comes in all forms and involves all sorts of people - sometimes including against family members.
It’s a sad day in a family when there is any form of abuse. Even the strongest of us can be in an abusive relationship - and we might not see it until after we’ve escaped it.
If you or anyone you know is in an abusive relationship, please get help - National Domestic Violence Hotline: 800-799-7233 https://www.thehotline.org/