There was supposed to be a withness and the police officer that in investigating a a friend of my sister and he told her everything this witness was supposed to have seen.
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.