The sister is not shy with her brother - he has known and used her body for a long time. She often bailed him out while he didn't have a steady girlfriend. Now he has a girlfriend, but he enjoys pleasing his little sister. And he always comes only in her mouth - she loves the taste of sperm.
Apparently the husband had his wife so worked up that she was ready to put any hole in her body just to have a rest, so he found a neighbor, whom he periodically fucks in her presence. At the same time she is completely uninhibited, and gives in the ass, and in all the slits that he asks, because his large cock she likes thoroughly, judging by her moans, even more than thoroughly.