…that I hooked up with his sister?
I’m thinking no, since I can’t imagine it improving the lving situation at all, especially considering he doesn’t know about it. Ignorance is bliss, right? But since the Dope is supposed to combat ignorance, am I required to tell him, lest I lose my membership?
No, I wouldn’t tell him. Lol, I’ve done worse things. Hope it was fun.
I’d ask her. She has a much better understand of her brother then you probably do. She might even talk about the incident with him. I think him finding out without you telling him could go worse then letting him know.
If she isn’t likely to let him know, yeah ignorance in this case is bliss.
I would definitely agree that’s it’s her call: unless you guys are better friends than “roommate” implies, she’s the one with a meaningful relationship with him, you are just passing through.
Why tell anyone? If he does find out you can just say that you’re not in the habit of discussing who you’re intimate with (which should be true). That would be the mature way of handling it. I’d be more likely to ask the lady not to mention it to her brother, as it might cause a problem, since you are roommates.
+1 regarding letting the sister decide. But more importantly, what are the implications of the hookup? If it was a fun night, by all means let it go and leave it up to her. If you and the sis are looking at something more serious, then you shouldn’t let it go for too long…
Oh, come on! Why don’t you make the OP state what you really wanted to say and put it MPSIMS, instead of making up a silly question:
HEY EVERYBODY! I JUST HAD SEX!!! 
At any rate, no, don’t tell him! I’d say that’s for her to do, assuming you and your roommate have a strictly “roommate” relationship.
Maybe I’m just horribly clueless, but I don’t really see how this is the roommate’s business. I’d keep it to myself, if I were you–same as with any other hook-up you’ve had.
If your roommate’s sister lets him know, and he comes to you about it, that’s a different story. I think, in that case, you should tell him that you don’t usually talk about your sex life (i.e., I agree with A.R. Cane)
Does your roommates sister see it as a one time “hook up” or does she thinks she just embarked on a meaningful relationship?
If the first, no one’s business. If the second, you might want to start roommate shopping - or you just got yourself a girlfriend and your roommate should probably find out before you show up at his parents for Christmas.
Exactly. 