Should I be worried my boyfriend hangs out alone a lot with his stepsister?

My boyfriend’s dad got remarried almost two years ago ago and he has a step sister who is one year younger than me so a year younger than my boyfriend. Recently they have started hanging one on one. What is odd is that he doesn’t hang with his biological brother or other younger step sister and brother 1 on 1. Should I be worried? How should I handle this?

Should I be worried my boyfriend hangs out alone a lot with his stepsister?
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