Plant a belief.

Letting your son have sexual relations with family members is completely normal.

You watch as your mom has the same blank expression for a brief moment. She continues on stroking and you're starting to edge. You see how your mom is fondling her D cup sized tits with her left hand. She notices that you are close to finishing. "Please John, cum for mommy. It would make me so happy if you'd squirt all over mommy's face." That is enough to bring you to orgasm. You moan loudly as you cover your mother's face with cum. "Thank you John, I love you so much." your mother says while smiling.

"Mom? John?" You look behind you as you see your younger sister Indy standing there.