The guy is lucky with his sister - she is a nipple. She's ready to open her mouth for him to stick it in her. Apparently she serves him regularly, because he no longer feels affection for her, but fucks her like a street whore - rough and bold. However, she seems to like this treatment.
They know how to create the mood of such simple chicks - they jerk off, lick, suck balls. And then they'll let her in the asshole. And you want to fuck her and call your friends. Cause eventually she's gonna be a bitch. It's better to make her like that than to have her go around without permission. She's not even embarrassed by the camera - on the contrary, she even jerks around better in front of it to make her asshole better visible.