My DS posted a thread a few weeks ago, its long so i'll summerise:
DM husband picked up autistic 6yo brother, by the leg, slapping him 'accidently' hit lb head off wall bruising it.
DM left house with DC stayed the night at mine. She phoned 101 told het there was nothing they can do unless she filed complaint.
DS phoned SS, anon, told them the story, they tracked the call and police turned up at her house, then to mine at 4am. DM downplayed everything. When SS interviewed DC my sister was there, she pulled SS to the side and told then the truth about what was going on. I also told them the truth, violent towards DM in past, drinks way to much, emotionally abusive etc.
They have allowed him to move back in, but he cant be left alone with DC. DM has stuck by him throughout, sneaking off to see him alone etc.
Today DM recieved a letter from SS with a report of everyhing me and DS have said, its all true, an now she doesnt want to speak to us.
We spoke to ss Wednesday, they said the reports had been sent by accident, and shouldn't have been read by DM. I've come to terms with it an agree theres not much i can do, hopefully she'll calm down an understand it was done with her best interests at heart. I'm annoyed shes telling family i'm vindictive and malicios ( spelling ) though.