Do you suspect your sibling is having premarital sex?

After reading the news article about how Malaysia is cracking down on premarital sex, it got me thinking about the this question. I'm assuming finding condoms in your brothers backpack isn't so bad--but if it's your sisters, you'd likely lose sleep. While you can't really scold your siblings the way your parents would, I'm sure if you suspect your sibling is having premarital sex, it would make you feel rather awkward. I have a sister and growing up, I tried sniffing around (not literally) to check if any sexing was going on. I'm not even sure how I would feel about it if I got any kind of confirmation. So do you suspect that your sibling is getting down? What are the clues and does it bother you?