Does birth order matter and how does it define who you are? Hilary Clinton is the eldest in her family but John Howard and Julia Gillard are the youngest. Malcolm Turnbull is an only child. The importance of birth order is often talked about. Most of us know the stereotypes: the responsible first-born child; the rebellious youngest; the spoilt only child. And then there's the so-called "middle child syndrome". But does the research back this up? And what happens when there is a blended family or complicated dynamics? Tonight we're trying to find out whether it really matters and how it may or may not help define who you are. Join Insight as we bring international and local psychologists together with a host of diverse Aussie families willing to share their experiences as we explore whether birth order shapes your personality - and what other factors are at play.