Poll: Dating Your Best Friend's Sibling: A Do Or A Don't? By YourTango EmailPrint Comment? Share on Facebook So that's why you spend so much time at Susan's. You love spending time with your best friend. And her hot brother is just conveniently always around. Would you try to date your friend's sibling or just be content with your fantasies? Poll: Dating Your Best Friend's Sibling: A Do Or A Don't?: A do. What could be better? You already know his sister loves you. A definite don't. You feel like her family is your own. It'd be too weird. It depends on how your friend felt about the situation.