Okay this is kind of a weird question, but I am wondering. I think it seems weird and gross now. Okay so I don't know how young I was (at oldest, 5 or 6. Somewhere around there probably), but my little sister and I were playing something that I think was sort so like "house," meaning I think I was a dad or a husband or something and she was a mom or a wife or something. I think she was supposed to be going to work or something. I think it was just for less then a second, but I think she kissed me on the lips (yuck!). Is this bad? Also would this be considered "a first kiss" because now I think it's just ... Yuck!
No, it would not be your first kiss of this type since I'm sure your mom and aunts have all given you kisses, especially when you were a baby.
You were young and imitating what you have seen grownups do. At the time you had no idea what those things meant, which is why we talk about the innocence of childhood. Now that you are older, you understand meaning, which is why you reject the idea. But nothing wrong happened then.