I'm dating this guy, and I found out I used to date his sister, but I didn't say anything right away. It's totally random, 'cause when I was with his sister a long time ago, I didn't know I would be gay one day. It wasn't long with her, but now I'm with her brother and I really like him. I think I need to tell him before he wants me to meet her. I did it with her; do you think he needs to know that?
Keeping It in the Family
Holy coincidence, Batman! You've landed yourself in an unusual circumstance. But don't fret — it's not so strange that you can't work though it. And it's not your fault this has happened. Sometimes fate just has a funny way of working.
Your instincts are right: You need to let the cat out of the bag before your guy tries to introduce his sis. You've kept this secret long enough.
Relationships that stand the test of time are built on trust; don't start off with a major fumble. Be up-front right away, and there's a good chance he'll see this for what it is — bizarre serendipity. If you were to keep mum and he found out, he'd likely feel uncomfortable, vulnerable, messed with, weirded out — a whole host of unpleasant emotions you don't want to cause.
Word to the wise: Don't divulge too many specifics, unless he asks and you feel ready to share all the deets.
And what about his sister? You're not responsible for their relationship, but it's important to consider that she may not take kindly to sharing her past with her brother's present. Hopefully she's open-minded enough to support your romance — after all, she liked you once! Maybe she can again in a new context. I'm crossing my fingers that you two ended things amicably.
Honesty is the best policy. Good luck — we don't need any more drama here.