Does this say anything about my sister and i?

Okay Ive been tripping out about how my bf and sister have a lot in common. From their look to what they say...its scary and yeah awkwardly I have a feeling that once we all hang out, they might get along too much. But on the other hand, her bf and I seem to also be similar. Like I get where hes coming most of the time, the things he says or does I can relate to. I wouldn't say my sister and I are opposites, in fact, we are more similar than different which is why I wouldn't be suprised (again awkward) if my bf were to grow feelings for my sister since she's almost like me. But I was wondering, considering my sister and I aren't that different, what does my bf and her being similar and her bf and I being similar say about my sister and I's relationship? Does it say we like each other's personality which is why we're going out with guys who remind us of each other? Does it say that opposites def attract within our relationships with our bf? Idk its too ironic to be normal.