That's what a personal assistant is for, to always be there when the boss wants her to be. And to do what he demands. This man wanted to relieve the tension - the assistant was at hand, without hesitation and took advantage of her. According to her cries and sighs conclude - this is the work she likes!
What an enterprising brother, the other would have asked for money, but this one only needs to put his dick in his sister. And she's not too shabby, she kind of paid off, and kind of had sex for fun!