Cowgirl

You wait until Sis has made Rachel cum and then you call her over. Your sister seems a bit **** "I was having so much fun testing out your new property" She whines. You smile and reply "Rachel and Sharon sure are wise investments aren't they? But you know, sis, I've been feeding you my cum and piss all these years. I think it's about time you do something for me, don't you think? See if you are as much of a wise investment as they are."

Your sister looks up at you and then resolve enters her eyes. She starts licking your dick like the good little sister slut that she is. Once you are at full-mast she lowers herself down on top of you. "I'm so thankful for all of the investment you've put in me, please let me show you how much you mean to me."

She starts to ride you like the well trained bitch that she is and you smile up at her. "Oh, I know how much you need me. But in order to prove it the whole world I'm going to knock you up!" Your sister moans in arousal. "Only you can knock me up. Your cock is the only one for me." You grin at your sisters submission and pull her head down for a kiss as you release your cum into her fertile pussy.