You take the consolation prize.

“Kary, you aren’t even trying!”

“I am trying! Look, it’s like sticking a log in a pencil sharpener! You are going to get another dose of my cum up the ass if you keep pushing!”

You keep pushing! You loved getting your sister’s cum in the butt last time and you want it again!

“Bro! I guess we are doing this again?” Kary doesn’t wait for you to acknowledge.

You put your hand on your big belly to gauge its growth again. Your sister is going to be out of cum again after this. She will need to be fed again. Or you can just wait for her to recharge as you digest.