If you're a firstborn, you may have always felt like your younger sister is more genetically blessed than you...
Well, it turns out it's not just in your head, in fact, it has now been "confirmed".
A study, which looked at more than 26,000 Swedish women, revealed that firstborns were nearly 30 per cent more likely to be overweight than their younger siblings.
Ugh! How unfair ...
It's not to do with genetics though, it's purely because of birth order.
Jessica Simpson (right) and younger sister Ashlee Simpson (left). Photo / Getty
Haylie Duff (left) and younger sister Hilary Duff. Photo / Getty
As reported by Today.com, researchers suspect that conditions in a woman's uterus change after her first baby is born which reprograms metabolism and the regulation of fat for the next newborn.