It all started when Patty Halliwell took a fall down the Both Phoebe and Prue had moved away when they got old enough to, only Piper stayed home to be with her grandmother(Grams).
When she died all of them returned to stay in the house. During their first night together in their grandmother's house, Phoebe finds a book of witchcraft and recites an incantation that leaves the sisters three with powers they were destined to have.

Which created the power...The Power of Three

Prue had the power of telekinesis
Piper had the power of freezing time
Phoebe had the power of premonition

CHARMED