Autistic family memeber

So my parents had custody of my cousin who is now 19 funtional autism. Still lives with them but has become aggressive(punching, throwing things ect) he threatens ppl including my 3 yr old he will beat her head in when she does something he dosent like. My mom said he was going great so allowed my daughter to go with them a few hrs. I go to pick her up she has bad cuts on the backs of her legs. I asked my mom she acted so surprised she never seen them. 😒 i asked my daughter what happened she just kept pointing to his room. I love him and want him okay but decided it was time to draw a line she would no longer be keeping my children until she seeks help for him she acts like im wrong. She hides incidents that happens when my child is in her care and other family memebers tell me and she gets angry. I have the right to know what happens with my child there. She is putting me down and says it me being irrational because all my pregnancy hormones and im such a bad person. Am i wrong for feeling like my daughter isnt safe i understand its not his fault but i feel its my job to keep them safe and she can not be there without me anymore.