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.
The question, in my humble opinion, on the above video may sound as follows: is the sensation experienced by the girl really pleasing to this girl? Is it acceptable to her?