of course its absurd that alignment of the stars at birth can influence someones personality - carl sagain argued that the doctor delivering the baby has a greater gravitational effect on the baby than the closest planetary body mars
)
however, i think its perfectly feasible that the horoscope is correlated with various conditions that might affect human development. for example children born in winter will be taken outside less, and exposed to less sun, which may influence them for certain traits. different environments make even genetically identical twins develop differently.
a lot of people uncannilly fit their star sign... there might be something in it
.