My partners older son hits our younger son
My partner and I live seperately and has an older son (age 11) who behavioural issues. I've recently found out that he's been hitting our son we have together (age 4). Together she and I 2 children, the 4 year old boy and we also have a baby girl (3 months old). We have joint custody of our mutual children and she shares custody of her older son with his father. Shes kept this information from me and has made repeated excuses for her older sons violent behaviour. She's said she's "told him off" but as it's apparently happened a few times as she's kept it from me, 1. Her approach to dealing with the issue isn't working , 2. Her keeping it from me is lying and makes me not trust how often this has occurred, 3. She got mad at me for asking questions and became verbally abusive towards me saying I need to know when this happens. I found out as she slipped it out in a chat we were having and she didn't intend to disclose it to me. What can I do. I feel powerless to protect my son and potentially our daughter as she gets older as well. Any advice on my rights or advice on what I can do to step in personally or if need be legally would be much appreciated.