The Caine Family is a family that is mostly consisted of powerful demons. They are located in Hilltowne where their mission was to gain the power of the Source of All Evil so they can become the most powerful family in the Underworld.
Alastor was the patriarch and presumed to be the oldest member of the Caine family. He set forth a plan to allow his youngest son to become the host of the Source. However, he was vanquished by Macy Vaughn when she took on the Source instead.
Hunter was a powerful demonic assassin and the oldest son of Alastor. He was banished to Tartarus after attempting to use an amulet to drain the powers of the Charmed Ones. Later, he somehow managed to inhale the Harbinger of Hell and was broken out of Tartarus by Charity Callahan at the order of his father. He would eventually be vanquished in battle with the Charmed Ones, allowing the Harbinger's demonic virus to infect many innocents.
Abigael is the half-witch, half-demon daughter of Alastor and the witch, Francesca Jameson. She is the half-sister of Hunter and Parker. Abigael's father did not much care for her since she was a female, and she was raised by her mother in Sussex. When she was thirteen years old, she reached out to her father since she was curious about him and her demonic side. Alistair sent assassins with the ability to kill anyone that they touch after her which left a negative impact on Abigael, who survived the ordeal.
Parker is a half-demon, the younger son of Alastor and his mortal ex-wife. He is the half-brother of Hunter. Since he is a demon born of a human, Parker is a potential candidate to become the host for the Source. Therefore, Parker's father wanted to release the Source so that Parker could become the host, making their family the most powerful in the Underworld. However, Parker became conflicted when he began grow feelings for Charmed One Maggie Vera since releasing the Source involves hurting the Charmed Ones. Alastor's plan ultimately failed, when Macy Vaughn took on the Source instead.
Julia was the mortal ex-wife of Alastor and the mother of Parker. It is implied that she did not know that Alastor was a demon, until she began to experience the demonic effects of her pregnancy with Parker. She was killed by Hunter as part of Alastor's plan to lead Parker into taking on the Source.