السلام عليكم ورحمة الله أحسن الله إليكم I am a revert of 3 years and the only muslim in my family. My sister recently got a boyfriend and is always bringing him over to our home to stay over. I feel if I'm too harsh on my sister I might close the door for da'wah forever. How do I deal with this?

Her not being a Muslim is worse than bringing a man. Therefore, this is not what you should be concentrating on. What you should be concentrating on is trying to lead your family to Islam. Obviously, you don't have much control over their lives because, for them, all of these things are allowed. You have to be wise about it: if you cannot change that which is haram, then don't push them away from Islam.