Am I wrong??

Ok so I have 6 kiddos who are 3,4,8,10,12,15. We are a former military family. And every where we have moved my mother has followed us. I am very close to my mom and so are my kids. I have 2 other brothers both whom are addicts (1 on alchohol the other heroin). My mother has always lived alone. A year ago my brother went to prison for a number of charges. He recently got out about 3 1/2 weeks ago and moved in with my mom. Not even 6 days passed before he went MIA chasing his black dragon. He convinced my mom into coming to pick him up swearing he was sober and he only used 1x bla bla bla. Well yesterday he decided to start using again. And my mom told me today and I told her I was sorry but my children will NOT be coming over no more as long as he is there. Neither will I, this upset my mom and she basically hung up on me and now wont answer me or respond to texts. I feel like any good mom would do the same. I dont want my kids around my brothers at all. I dont wan t them exposed to this kind of shit.