<human>: Can you summarize the given text in a few sentences?

Thanks everyone. You are very helpful.

I called my grandparents on Saturday afternoon and told them everything. I had taken a few pictures from my sister that night and emailed them those pictures as well. They were pissed off and angry at him and my mom for not standing up for us. They told me to stay upstairs and don't apologise and they will come over on Sunday morning. So we did that. My mom came to talk to us again on Saturday evening, insisted that we can go apologise and we can all forget that it happened, but we kept refusing until she gave up. Later that night my mom came back up to talk to me again and wanted me to end this "rebellion" as she put it, saying that it won't lead to anything good and it just makes things worse. I told her that I'm just protecting sister. She said "it's my job not yours". I said "clearly you're not doing it well enough so I'm gonna have to do it". She gave up again. 

So grandparents came over on Sunday morning. Mom and step father were home as well. We were upstairs and couldn't hear what they were saying but I could hear that my grandparents were very angry. I don't know what happened but after a while my mom came up and asked us to come down. We went down and Stap-father apologised to my sister and said it won't happen again and that he will make it up to us. My grandfather told me to let him know ASAP if something like this happened again.

After they left my mom looked very angry at me but didn't say anything.

P.S. I didn't call the police in the end. I was afraid to make the situation worse and make a much larger mess. I though involving grandparents is enough and they know better whether to call the police or not.
<bot>: I called grandparnets. They came over and talked to them. Step father apologised after that and said it won't happen again.