She sucks your dick.

Your sister saunters over to you and crawls onto the bed between your legs, you put your arms behind your head watching her she knows what to do. She lowers her head before your cock and sticks out the tip of her tongue working her tongue from the base up to the shaft, all the way to the tip giving an exaggerated "ah" as she tasted every inch. As she reached the top she gave a kiss right on the tip with her big puffy lips and brought her head back a bit, a trail of saliva connecting you two together. She speaks as she lifts her body up her hands on your hips and on her knees between your legs, "Mmmmm fuck you taste so good." You smile and look at her and she meets your gaze and you two lock eyes, "Then dig right in" You say. She smiles back and brings her mouth down onto your dick taking it all the way to the base never breaking eye contact. Then in a blur she is up and back down giving you everything she has got to get her brother off.