Middle child Syndrome

"We don't have a favourite" I think this is the biggest lie my parents have ever told. In the beginning it wasn't obvious it still may not be obvious to other people but I see it, I live it. It's a joke, a sarcastic thing people say "middle child syndrome," but it eats away at you. What does it mean, I still don't have a real answer or I do but its my answer related to my idea of being the middle child, my idea, my childhood well my entire my life.