You two share a really similar approach to life. People tend to view the two of you in similar ways, and you both have the same ideas about how to operate in the world. Socially, you have similar instincts as well, and also sexually.
Your needs in a relationship, your outlook on life, your interests and your goals should all have quite a lot in common. For all these reasons and more, you probably get along really well! You understand each other's instincts and urges, and you're usually on the same wavelength. You need similar balances of intimacy and independence; you have similar ideas about spirituality; you love the same kinds of movies, discussing the same kinds of topics... Of course, this can present a problem in the sense that you match up the negative ways as well as the positive ones. A gloomy outlook on life, an indecisive nature, a flaky approach to work or finances ... Any negative qualities are shared between you, and could magnify themselves when you're together. On the other hand, you're able to make leeway for each other's flaws that other people might never be able to make! So it all probably works out in the end. On a day-to-day basis, you get along great, and you have similar instincts and timing. This aspect helps smooth over any other more difficult ones between you that make it hard to get along.