In my experience, sometimes family members don't even want to admit that domestic violence occurred, even when you're telling them about the experience as an adult.
They may try and straddle a neutral line by saying something like "I believe something happened." This happened to me as I tried to tell a family member about the violence I witnessed as a young child. Since it was their brother who committed the violence, you could kind of get the feeling they were on their brother's side.
They even brought up the issue of "false memories" (normally applied in the context of sexual abuse) and how I may have thought I saw something that may or may not have occurred. It may be a lot to expect them to condemn their brother, but certainly if they wanted to stay neutral, they could have simply said they weren't there so how could they know what happened. That's my rant for today.