Not sure who else to talk about this☹️

Sorry in advance for the long post but did not know who to ask for advice. I’m married and a mother of two. Currently pregnant and we just bought a house. We were living in an apartment before but working on fixing up a few electrical issues with our new house so decided to stay for a couple of weeks at my grandmas and my sister and her boyfriend live there. They do not have a good relationship at all, always fighting, taking their baby away from one another, and always calling the police. My sister always takes him back the next day. My grandmother of course allows it as she says that she doesn’t want to ask my sister to leave and has never said anything to her boyfriend. My husband wants nothing to do with my sister and that drama and I understand but for me it’s a little hard to cut her off. Anyways a few days ago my husband came home and found a bag of my clothes including underwear along with his pack of cigarettes and lighter. We thought it was weird and I asked my sister and she told me that wasn’t her bag and didn’t even know. Yesterday while my sister and boyfriend were fighting he broke her glasses and she asked him in front of me ‘do you want to know what your clothes were doing in that bag?’ i of course said yes and she went on to say that he dresses as a woman with my clothes because he was molested. I didn’t know what to say. And I don’t know what to do? The fact that my sister knew it was going on and she didn’t mention made me upset and I can’t tell my husband anything because I know how mad he would be. I don’t want to start problems but I do not feel comfortable here or even talking to her. Any advice please?