Sibling retaliation

Take that, all you younger siblings out there. Sure, you get everything you wanted growing up but how's that working out for you now? In all seriousness, issues of birth order are fascinating, but I am always a little hesitant to accept the findings of studies like these. With the many factors involved in human development, can birth order be isolated so specifically? Even more, is there something deeper working in familial relationships that is producing these results?