1) genes from parents and their combinations and activations based on:
a) health / happiness of the mother during pregnancy
b) climate experienced during pregnancy and birth, (earth/sun relation – affects Vitamin D) which is affected by:
i) time of year while in pregnancy and at birth
ii) location on planet
iii) habits of mother in relation to climate (indoor climate controlled compared to outdoor)
c) position of moon cycles during pregnancy and birth (water rise and fall patterns may or may not affect sinus pulse in brain)
That’s as close to astrology as I can go.