Disfunctional stepfamily situations! Husband says "Don't bother me, I don't care." Pls give yr input?

Full custody step mom of husband’s 5 kids from prior marriage, ages 12-22. All immigrants & Muslim,12yo is only girl, treated harshly since she is both female & the youngest. Their home country still does genital mutilation of females; husband lied to me about that (and many other things resulting in me being in this situation). And Muslims R not known to be pro-female. Example of a recurring prob: Girl is in living room & starts to play loudly. Her 4 brothers ages 15-22 are super loud but they seem to notice it more when she is. She is talking to me later about something when the 22 yr old comes out of the bathroom & hears the complaints of his brothers about her. He angrily interrupts our conversation & tells her in their language to go to her bedroom & not come out. I say “Um, do you need a timer.”? He says no. She'll stay for two, three hours without knowing the deadline & says it to me in a case-closed tone. Husband says “What's your problem with that?!" and "NO counseling ever!"