Is it weird to have feelings for my stepsister who has a boyfriend?

This girl is a liberal (self-proclaimed "moderate") agnostic who voted for Biden and her mom (my stepmom) is a conservative Christian who is married to my dad who is a libertarian with mostly social liberal views (though he voted for Trump just like my stepmom). This girl, she's 23, she has a boyfriend (she's had at least three as far as I know). The other stepsister is just 20, and she also has a boyfriend, but she's also a Trump voter, but I'm not as attracted to her even though I also voted for Trump.

Why do I find myself more attracted to liberal girls than conservative ones?

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Another thing too, I DO NOT live with them. As a matter of fact, she lives on her own and she sees her boyfriend after work. I NEVER openly develop any romantic or loving (beyond family) interest in them.
Is it weird to have feelings for my stepsister who has a boyfriend?
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