Looking for a doujin with a girl like this pic. It was about a foreign step sister or something going into a Jap family with a brother and a sister, and the brother ended up forcing her and his other sister later into sex. I think they were both blondes too, I don't remember how the guy did it but I think he threatened to rape his other sister.
Also pic is Kareshi Friend Boyfriend, thanks guys.
http://readhentaimanga.com/i-want-to-be-your-bride-even-though-im-your-sister-english/1/1/
this? i feel like i've seen what you're describing recently..