Landlord allowing other neighbor to use their room for her unmarried

Dear sir my landlord is allowing her another tenant, my next door neighbor for unauthorized unmarried couples to use her room. They come at latenight, stay and go next day. I have teenage son and daughter. I feel insecure and unacceptable social trend. I have told landlord but she refused to take any action. Can I approach local councellor and other neighbors to stop this . The tenant has given threat indirectly not to disturb her activities. What to do. Can I file case against the tenant or both tenant and landlord