It's not all about being 'spoiled' or 'favored' (we all know the oldest is always the favourite).
I have 3 sisters, ages 31, 26, and 17, whereas I'm 15. My two older sisters are half-sisters, but that's never been important to us. Because of the large age gaps, I've never been that close to my older two sisters. When I was younger, I had a really good relationship with my 17-year old sister, but as we grew up, we grew apart.
Being the youngest, people often look at you as the 'baby', which can be frustrating at times. In my experience, parents are also more over-protective of you than your siblings. But you wanna know what the worst part is? There are literally no pictures of you as a child. None. They figure, "eh, what's the point? We have tons of pictures of the other children, who cares about this one?" I mean, they probably didn't think that at the time, but that's what it sure feels like.