You know you are in love when you know. It's not about their actions, or even yours, if love exists, it is all ready there. It can be fostered to grow, but if you wish to do so, it must mean love is there all ready.
Examples of things you love about them don't truly matter because those are simply excuses. Even if you took those things away, you would still love them. If you can accept that, then it is love. If not, then it is only love of their actions and not of their being.