I've been told I have a "type" in men. Why is that, and how can I be more open to other people.?

As Iv'e grown through my teenage and young adult life I have dated a couple of guys. I was hanging out with one of my best friend of 10 years and her and I got on the topic of our relationships. While I easily noticed over the years that she has a type, I haven't really thought about myself. She expressed that maybe I shut people out if they don't appear to be my type, and now I am afraid that I do that.Her and I sat together and compared pictures and personalities of the guys I have ever had a relationship with or have been wanting to. I realized that all of them, with the exception of two guys, have similar facial features and attitudes. The scary thing is that most of these guys look and act like my father (who I absolutely adore).

Why do I tend to pick guys that look like my father? How can I be more open to other possibilities?