Okay, I've been dating my boyfriend (Jeff) for almost a year now and him and his brother (Tom) live together. Recently, Tom allowed his ex girlfriend (Stacy) to move in to their house (he dated her for almost 8 years and they've been broken up for about 2 years now; but they were an on and off kind of couple). Well, Tom is in love with Stacy, Stacy has a boyfriend that lives out of state and is not interested in Tom the same way he is in her; she just wants a free place to live, and to top it all off Jeff and Stacy have had sex a few times about three years ago..... So yeah. My boyfriend is currently living in a household with some chick he has banged. Tom does not know that Stacy and Jeff have had sex and would be crushed to find out. I know it was a while ago, but i still feel like she can be very flirtatious.. I don't know where to turn or how to handle this situation.. She goes in Jeff's bathroom and gets his dirty towels and wash rags and washes them, along with going in his room and taking his dirty laundry and washing them as well. I don't want to ask my friends or family for advice because i really don't want them knowing my business. Me and Jeff are great, we've talked about marriage and i really feel like he is the one. He treats me like a princess and i do trust him. I just don't feel comfortable with him living under the same roof as this girl he has banged before. Advice, please.

Your BF's brother and this girl split up 2 years ago after an (almost) 8 year long relationship..
This dude stepped on his brother, who I'm guessing he is also quite close to, seeing as they live with each other? Who is to say he isn't screwing you over as well?
I think he boned her. Ballsdeep.
Screw it, get back in touch with Stacy and just have a full on orgy!
Pics pls.
But wtf your bf slept with his brothers gf? Fucking tool. And your jealousy is normal
Sounds like she's looking for some validation because for whatever reason she's threatened by you and trying to make herself seem "better".
I lived in a house where the main signer managed a store, there was a girl who worked under his management living with us too. and she fucked him because.. well, she was a skank and sometimes she got away without paying rent on time. The thing is she also slept with another roommate, and at some point she started flirting with me. Which was very disgusting. So, maybe I'm wrong, but I hate that type of girls.
...but...
As a lazy guy, I'd probably let a female friend that I'm not interested in live with me if she did my cleaning and laundry.
Here is mine: Most couples break up over such a thing because they never discussed it until the point came when accuses just come out, mostly without the other person knowing why and from where they come. The other person goes defensiv etc.
It's a recipe for disaster!
Talk to him, without accusation. (I guess he was the one who told you the whole story with the three of them, that is a big show of trust on his side, still: TALK TO HIM!!!)
But honestly i guess if he loves you two can talk abt it..A healthy conversation will surely help..