Likely answer

The Secrets of the Immortal Nicholas Flamel: Twins and Magical Mentors

The book you are looking for is "The Alchemyst" by Michael Scott. It follows twins Sophie and Josh Newman, who discover they have the potential to use magic. They are mentored by the legendary historical figure Nicholas Flamel, who has stayed alive for centuries using alchemy. The series features many other historical and mythological figures who possess magical abilities.

Confirmed match: The Alchemyst by Michael Scott