Is There Such A Thing As A Soulmate?

Everyone always mentions the word soulmate to me and I always wonder if it is true that there is this one person out there to foot the bill as a soulmate? To be someone's only soulmate in the world is a hard thing for me to come to terms with and for them to follow and live up too. So is there just one?
A friend of mine said to me the other day that she is worried about me, because I am single. It's funny because this exact friend is single as well. So to hear it from her was a surprise and kind of contradictory. I asked her why she was concerned about me and she said well you are always saying you don't want to get married and have kids. She already has children from a previous marriage so she already has that part finished in her mind. My answer to her probably wasn't something she wanted to hear. I told her one not to be worried about me and to worry about herself. I do not think anyone should be concerned about others unless there is a major crisis going on in their lives. I also told her that I do not need a marriage or children in my life to fulfill me. 
Ever since I was a child my parents always knew I wasn't looking for the storybook ending. I was always more concerned with what I wanted to be in life and what I could do for the world and people than my stake in life as a wife and mother. There are just some people in this world who shouldn't have kids and I feel right now that I am one of those people. Now if I change my mind later in my life than I do, but for now it's how I feel. And I shouldn't be punished or looked upon in a weird way because I don't want that in my life. 
I also told her that soulmates for me are many people in our lives. I feel we are supposed to be here for people for a certain time to help them out during a transition or for them to help you through a transition and then you move on. Until the next soulmate comes along. I know some people won't feel the same way and that's ok. That's what makes the world go round. But I shouldn't be penalized because I prefer to be single than in a relationship. I could look at the people who are always in a failed relationship after failed relationship and say something about them, but I don't because that is their path not mine. So eventually my friend will see what I am talking about or she won't, but either way I am still going to live my life the way I want too and not the way I am told too or how the world thinks I should.