As silly as it may seem, you can be charged with and convicted of domestic violence for pushing a sibling. In this case, theoretically both of you can be charged and convicted. If you can, hire a criminal lawyer who can help you. As crazy as it sounds, if police are investigating the case, it's possible that you might eventually have a warrant out for your arrest for this "crime."
I hope what I've written here helps you, but remember, this answer isn't legal advice and doesn't establish an attorney/client relationship between us. To get actual legal advice, you need to speak to a criminal defense attorney.