No co-founder is perfect. I've never met a serial entrepreneur who starts new companies with the same people.
When my co-founder relationships have worked, it's been because we're on the same page professionally, not personally. I like them and enjoy working with them, but they're not my friends, and I don't rely on them for anything other than their role in the company.
If your co-founders are also a large part of your social life, things can get a lot more difficult and complicated, and friends are rarely the best co-founders anyway.
