I found a used condom in my nieces room along with her boyfriend when I stopped !

Like most of the people who answered, I'm appalled that you had to ask. What you should have done should have been done right there. And that is to get the 16 year old to give you his name, address and parent's name, scold your 11 year old niece, save the condom as evidence for the courts (icky!), call your Uncle and sister to get home immediately. Your being afraid of what people will think about you is nothing compared to the path your niece is chosing. In the long run you would have saved her. Good luck!

11 years old!! Thats extremely disturbing, I can't believe you didn't do anything. It's common sense to kick the boy out and inform both of their parents, but you would rather allow an 11 yr old girl to have sex with some highschool boy than cause much needed disciplinary action in the house?

11 is to young for it to be consensual anyway. The course of action is obvious in my eyes. The parents and police should be involved in this. He is 16 and she is 11. To me that is WAY different then if she was 16 and he was 18..,
11, wow. you should have done something right then and there.

Kick her butt. And when you're done with her, kick his butt. And when you're done with him, find his parents and kick their butts.

sex is only natural

shes only 11 and shes with a 16 year old its time to start world was 3

You should talk to her. Why does she have a boyfriend at he rhouse anyways. she is 11 !?

These type of things are embarrassing so talk to your sister first. Don't let the whole household and everyone know. Embarrassing her won't make her stop, it'll just make it worst because she can't take back what she did. You definitely don't want to go to the cops and blow this out of proportion.
If you embarrass her too much, she will have little shame left, and she'll just despise you and your sister and possibly rebel and go out of control even more later on. I'm not trying to downplay the whole situation but at least they used a condom!

Talk to your sister, talk to your niece, talk to the guy. Don't try to break your niece up with the guy but try to get the guy to break up with your niece. He's more mature so he'll understand it better.
Tell him just 5 years ago he was just 11 and he's probably grown and learned so much in those 5 years. But you might want to break it down some more, like 16>14>12>11 so they can better understand it.

Make sure they're paying attention as well when speaking to them because kids tend to zone out in situations like this. Don't be afraid of talking to your niece about sex/pregnancy (or get your sister to do it.) I know these things can be embarrassing and awkward to talk about and people tend to rush it and kids don't learn or worst case scenario is when people get cops involved because they don't know what to do. The guy is 16 but remember that he's still just a kid and i'm sure in just 4 years 16>18>20 he'll learn and wise up a lot.

I've been in that situation before but I was 15 and the girl was 12. No cops involved but the mom had a good talk with me.

When I was young and dumb.