My boyfriend likes his step sister. help?

So my boyfriend is twenty six, good looking tall blue eyes so most girls like him. His only sibling is his older bro. They grew up with their dad and recently he started dating this Latina women. We all went to dinner to meet her kids and she has this daughter that’s 19. She’s very attractive and I could tell he thought so too. I’m blonde tall and slim she’s Latina shorter and curvy but fit like how the fuck! They were flirting right in front of me. He claims he wasn’t but I can tell she likes him. He’s staying at his dads for a month then he’ll be traveling back to Florida. Which is where him and I live. I’ll be leaving tomorrow and I’m super paranoid. What should I do
My boyfriend likes his step sister. help?
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