Having watched a number of my nephews, neices and cousins growing up I would agree that their general personality was observable, even from a very early age. As one who believes that we are all eternal souls I wouldn't put this all down to genetics.
I have also witnessed people who have gone through radical changes in their established long-term behaviour (i.e stopping bad habits, from negative to positive attitude etc...) although their character remained in some ways consistent throughout.
... Neemai
