My uncle's friend has two beautiful daughters. I know them, but not very well. And I want to invite one of the sister to the movies, the elder one. She's two or three years older then me, and the other sister is my age.
I think I'd offend that another sister if I don't invite her too. That's the problem. We're completely different and will have nothing to talk about. Plus I can't keep conversation with two girls at a time.
What should I do?

P.S. It's not going to be a date, I just want to spend time with her as friends. But I want to be alone with her.

You're not fucking them. So why have to hide? Invite the sister you like to do something only two of you have in common. Her sister will understand without you having to explain. If she gets offended, just be honest and unapologetic. Tell her you have more in common with her sister.

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