There are people you meet who you know you're strongly attracted to, there are those that you know you're not attracted to...
And then there's a big group of people who you're uncertain about. This includes people who don't have the features you're normally attracted to, and people who you don't even really notice. It may include people who you don't think you're that attracted to (which is different than knowing you're not at all attracted to them).
With people in this last group, you can definitely end up liking them as you get to know them better, and ultimately finding them much more attractive than when you first met them.
Yup. They're my ex now and we were not right for each other. But you know, I realized that someone can become more attractive to me if they're funny and charming. This guy grew on me. I thought he was alright looking, but his personality was great.