I believe my SIL killed her children

I'm not sure where else to go with this so thought I'd put it here. This is a throwaway account.<br><br><br>My SIL 'lost' 3 children before they made it to 2. The first death was when my SIL and her husband were newly married. Their first child was born 9 months after their wedding. Nothing unusual at the time except it was a very early baby. Anyway he died after 8 weeks in a tragic stair accident. The family were devastated. But it was a tragic accident so you moved on.<br><br><br>Their second child was my niece. She's an adult now and lives with us occasionally and stays with other family members and friends. So she's safe. She's had a lot of issues, physical disabilities etc but nothing that should have caused her harm. When she was 3 my sil had her third child who sadly died in a drowning accident.<br><br><br>The police investigated these two incidents and my BIL was charged over the drowning accident. His career was over and he's never worked since. The case collapsed after 2 years and he got a large compensation payment from the police. <br><br><br>My SILs 4th, 5th and 6th children are my partners nieces/nephews. Numbers 4 and 5 are adults now too. The 4th child is the golden child. They do everything right. Never had any issues. We don't see them often but know they are doing everything they should. The 5th child is more difficult. They were in a traffic accident with their parents when they were 8. Suffered a head injury and has had a lot of physical disabilities and mental issues ever since. The accident happened when my BIL lost control on black ice. Nothing untoward. Just a tragic accident.<br><br><br>The sixth child died from SIDS a year later. Unfortunately this was the first time I'd met my partners family. I was in my 20s and totally lost and didn't know how to deal with the whole situation.<br><br><br>After the baby died my SIL decided to foster-to-adopt children. Three siblings came to them after the baby passed away. The first few years were really tough for them. But you could see there was a marked improvement in the kids and they thrived with my SIL.<br><br><br>Then their 7th child was born and then their 8th. Each in separate years. Both died from SIDS within 6 weeks of birth. Their fostering failed after the first SIDS death. Social services accused them of being neglectful parents and the foster kids were removed. My SIL and BIL have never spoken about it. But my niece told me what happened. It must have been horrific as my BIL hasn't worked since.<br><br><br>The 3 children they have are young adults now. <br><br>Then my SIL started adopting. They currently have 8 children. And 4 dogs. And my niece. My niece stays with them a lot as they think it's best. It's never really worked out long-term. But she was with them until last year when they kicked her out. They said it was because she was interfering with the younger kids and made them unsafe. We've taken her in occasionally. She doesn't want to live full-time with us. She says she loves living with her parents, even if they're a bit strict. Some of the things she's told me make me think they're abusive. But she always retracts these confessions and says they're lovely and that I'm making her badmouth them. We only found out she'd been kicked out because one of her siblings posted on Facebook saying how great it was that my SIL and BIL had raised another child to adulthood. It turned out to be my niece. They'd never told us.<br><br><br>The kids they've adopted have had a lot of issues. They all have disabilities and some behaviour issues. You can tell something is not quite right with them but they all seem happy enough. A couple of them have been in and out of hospital over the years. My SIL has talked about suffocating and being unable to cope with screaming kids. She's always been dismissive of her children. And makes them do a lot of the work for her. But she's never unkind to them. Or my niece.<br><br><br>Last week my partners family came to visit. My niece was staying with us, so she joined us. My partners mother made a comment in passing about my SIL having 16 kids in total. SIL replied that 14 was her actual number. My niece went and sat in another room on her own. <br><br>We talked to my mother-in-law about the comment. She said she only knows of 14. She thinks my niece might be the 14th. But there have been others in between. My niece remembers a baby dying in the night. She doesn't remember when or how old she was when it happened. My partners mother doesn't know anything about it.<br><br><br>I don't know what to do. I believe my SIL killed her children. I believe she is a danger to the children she has. And I know she's done something to my niece. But I don't know what to do. I think my BIL is caught up in all this too. I don't know where to go with this information.