Your " predicament " is only a set of " options" . Seems you have choices...Some guys don't have that. Younger sister, older sister, Mother Cougar...Dad, if you're that way inclined. Choose one, act. Get laid or fail trying. It's only a game anyway since you aren't really invested in any of these people.
doesnt seem delicate to me move on, if you want, sure text the sister if you think she'd be ok with that