Nice couple and they had a good time. Oral caressing in the 69 position is a real hoot. As for me - it is possible to stop here. You don't have to do sexual acrobatics every time. Quite a normal way for two to enjoy sex. But more often in this option, the first to cum is a woman. So then in any comfortable position, you catch up with yourself. It is best to lie on your side - when you come you can leave your dick in the car and lie there for a while more relaxing and stretching your pleasure of having a woman.
The sister is really uninhibited. Judging by the reaction of his brother and his unwillingness to break away from the game, his sister is already bored with him to say the least.