@Philippos,
You'll probably find the answer for Aristotle here on Google under:
Aristotle -biography ; the opening sentence says it all:
Aristotle, one of Plato's greatest students, was born in 384 BC. Aristotle's father was a physician to the king of Mecadonia,
and when Aristotle was seven years old, his father sent him to study at the Academy.
To be in the educated upper tier of society probably helped.