Am I doing the right thing?

Ok so real quick my brother in law just moved here from Florida with his son his fiancé and her son before he met her he was amazing y’all but then she came into the picture and it’s been hell! He went from looking healthy to loosing a shit ton of weight and even muscle tone. He’d had a problem with drugs in the past but since him and his ex had his son he’d cleaned up his act. Her on the other hand all we know about her is she claims her sons dad was a cop that went dirty started doing the drugs he confiscated and ended up oding she makes it look like she had nothing to do with it and it was always him that had the problem. Well the first time we met her wen they came to visit my mother in law had 50 pain pills go missing my brother in law said it was him but she had been boohooing about her wrist hurting and had gone to 3 doctors in the week they visited. Every time they would come something would go missing and they’d always be making excuses to leave every hour or so and they were always realllllly hyper and talkative. So anyways when they moved here in June me and my hubby were suspicious to say the least and then my 4 year old walked up on them smoking pot. I went off I know it’s just pot but I’m sorry I don’t want it around my child well it was getting bad so we told my in laws and shit hit the fan against us. My brother in law showed his true colors and I was just blown away. He sat there sobbing “I’m so sorry” around his family but then when I tried talking to him with no one around he sat there totally straight faced “it’s your gd kids fault for walking up on Shelly she should have minded her own damn business” (Shelly’s his fiancé) I was literally shocked he did a complete 180 from how he was acting not 3 minutes prior. It showed me he didn’t care what he’d been doing or that my child had walked up on that shit and I’m sorry but I don’t believe it’s just pot he has a problem and I don’t want my child alone with him or his fiancé. The day after that shit went down he comes to me and is like hey we’re going to the park with the kids and wanna bring brook (my daughter) I politely tell him “I’m sorry but no” and he goes off demanding to know why and finally I tell him “I’m not having her alone with y’all after what happened” and he just goes off. That being said now he keeps sitting here pulling this shit where he looks at my daughter and says “ you ask your mommy to bring you over and drop off at our new house any time you wanna play knowing I don’t want her alone with them. What do I do am I a bad person from not letting her be alone with them? I don’t care if she’s with them supervised but not alone I’d never keep her from her family I just don’t want her alone with them especially with the way they’re acting. Neither one of them have came to me and apologized for that shit he did to my hubby and his parents but her nope she’s not said a word.