TW SA: What do I do in a situation like this?

A few months ago, I was at the beach with my husband and in laws. Everyone was drinking and having a good time. My sister in law got very drunk though and even though we were talking about college and student loans, she somehow turned the conversation into an argument with my mother in law about how terrible of a mother she was for hiding the truth about something and how her aunts and uncles were enabling it by not speaking about it either. We got them separated and I walked my sister in law to our car (my husband was sober and driving). At the car, my sister in law confessed to me that her uncle, who was at the beach with us, SA’d her when she was little. My heart broke hearing those words. Especially knowing that this man is always around. She told me she never wanted to tell her mother (my mil) because she knew she wouldn’t believe her or take sides with him. She told me she didn’t care if I told her brother (my husband) she just didn’t want to tell her mom. After we dropped her off at home I told my husband what she told me and let him know I no longer feel comfortable attending family events where he’s at since we have a daughter now. He agreed but was so close to telling his mom. I told him it’s not our story or trauma to tell. She’ll talk about it when she’s ready. He thankfully dropped it but it was never mentioned again. Fast forward to a few weeks ago, the uncle moves in with his sister who has 2 little girls. One is about 10 and the other is 2. He just sent a picture of himself and the 2 yo laying in bed smiling. Now I know this could just be an innocent picture, but with his past I’m uncomfortable. I don’t know what to do. I don’t feel like it’s my place to tell my sister in law’s story but I also feel like I have to say something to protect these two little girls. What do I do? My sister in law and I aren’t really close so I’m not sure how to even approach asking if she’d be willing to talk about it with her mom so she can warn her sister about him and to not leave him alone with the girls. Only reason she was comfortable revealing that to me was because she said she saw my scars from the self harm I’d done years ago and she knew I’d understand. I’m so heartbroken over all this.

@Hanah she wasn’t talking about the SA. There were many other things that happened in their lives in which my sister in law blames her mother for. Not the SA though.

@Kim I know I should! I’m just worried they won’t believe me since I’m technically like an “outsider”. They’re a very strong knit family. I know I’d need my sister in law to speak up as well and tell her story for them to believe me that he’s not a safe person for those kids.

@Lucy you’re so right! I couldn’t imagine doing it. I couldn’t imagine it being my daughter in their place!! I’m talking to my husband when he gets home and letting him know I’ll be contacting his aunt and sister to let them know my thoughts. The smallest is just a month younger than my daughter and I’d hate for anyone to withhold this kind of info from me.