Have the sisters share your cum.

You begin thrusting harder and harder into Michelle's cunt as she in turn rubs her clit faster and faster until she too cums again. You decide to join the girls in letting yourself go.

You grab Michelle by the shoulder ripping her out from between his sister's legs. Michelle's face is soaking wet from her sister's cum and you quickly push her beneath you and let your white cum join her sister's in covering Michelle's face. Michelle has opened her mouth wide and some of you cum drops down onto her tongue while some splashes around her face.

"Show your sister how much you love her, Susan," you say and Susan obediently gets up and begins kissing her little sister. Susan slurps up some of the stray cum on Michelle's face as well and the two sisters share your full load together.