I got an erection when I saw my sister in her underwear, please help?

[Anonymous]

I accidentally saw her in her underwear and she told me not to look and I went away as fast as I could. Though I noticed I got an erection from it, I'm confused. I wouldn't want to do anything sexual with my sister, why did I still get an erection anyway?

[Dallsimo]

Same for me : i got hard by looking at my stepdaughter practicing dance routine in her leotard... but i would never have sex with her.. m

[Anonymous]

Whoops... now you have to go back in there and fuck your sister.

[abc--123]

It's the law

[Asker]

Since when?

[Opinion Owner]

It's in the constitution.

[BillieJean1070]

Perfectly normal... just go about your business.

[CheerGirl38139]

Because you're a guy.

[DarkHumorRUs]

That's cause your penis isn't smart enough to know it's taboo.

[micheal727jovanie]

Its normal I saw my cousin naked once I had an erection. I was 13 its puberty

[abc--123]

Don't worry I'm sure your not the first and won't be the last this has happened to

[Anonymous]

Your a guy. Send me your sister's number. :)