The chick is used to being treated this way. The impotent husband lost her at cards. That's why they've been pulling her like a bitch all day long. And the harder the stake, the harder they drive it inside. Only the pussy is already so used to the new masters, to the abundance of milk - that she does not want to go back.
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.