Hunter and Parker are half-brothers on their father's side. While Hunter is a full-blooded demon, Parker is half-human. Hunter seemed to care for his little brother, until the point when Parker fought against him to protect Maggie Vera. Parker then assisted in banishing his brother to Tartarus to get rid of him.
After Hunter's return from Tartarus, the full demon aided in his father's plans to make Parker the host for The Source of All Evil. Hunter tricked Parker into believing that he had killed his own mother and that Maggie had become afraid of him. Their interactions came to an end when Hunter was vanquished by the Charmed Ones.
More than 20 years ago, Hunter's dad decided to marry a mortal woman and have a hybrid son. The marriage didn't last long, but Parker knew about the existence of his father and his half-brother from his childhood and continued to contact them after the divorce of his parents. However, it is still unknown, if Parker knew about the demonic nature of his male line since his childhood or not.
It is also not known for certain whether the relationship between brothers has been close in the past. But for unknown reasons, at some point Hunter began to take care of his half-brother, despite the fact that he was dismissive of mortals.
The brothers don't have direct interaction, but Parker tells Maggie a story that as a kid he wanted to to learn to good play the guitar as his brother. If he didn't lie to her, then the half-demon has known Hunter for many years (at least since he was a kid).
The brothers don't have direct interaction again, but when their father gets mad at Parker for a stolen scythe, he mentions that his brother also lose once in his errand. It probably means that he is subconsciously jealous that Alastor prefers Hunter to Parker.
Hunter defends Parker from their father's harshness. When Alastor calms down, the brothers look at each other, which probably means that the father is not the first time demonstrates such cruelty. Hunter doesn't like the cruelty of Alastor to his younger brother, but at the same time he agrees with father about the "weak human side" of Parker. Later, Hunter in the guise of a waitress is visiting Parker in the restaurant and instructs him to find a way to run an errand of father. Hunter likes to make fun of his brother, but he does it without malice. Parker doesn't feel joy from his brother's edifications, but he has no problems when Hunter touches him. It becomes obvious that despite the differences, they have a good relationship.
Hunter and Parker go to Bucharest to find the amulet on their father's order. But romanian priest unleashed the staff's powers when the demon brothers infiltrated his church. Parker shows anxiety about his brother when Hunter rushes to the priest, at the risk of going to Tartarus.
When demon was able to get the upper hand and then want to murder the priest, Parker asked him not to kill a man. Angry Hunter too rigidly responded about his humanity than it shocked his brother (apparently this was the first time older brother had spoken of Parker's human side in a harsh manner). Nevertheless, younger brother continued to beg him to abandon the murder, and unexpectedly Hunter relented and released the priest. Soon it became clear that older brother was waiting for Parker to leave, and yet he killed the priest with his own staff. It became clear that even though Hunter cared about his half-brother, he no longer intended to tolerate his "emotional weaknesses".
Within the episode brotherly dissatisfaction with each other continues to grow. Parker trusts his brother enough to ask for his help when Galvin's mark responds to him, but he doesn't like Hunter's sadistic methods. In turn, Hunter shows discontent when he realizes that Parker removes the amulet from Maggie, thus restoring sister's powers. Contrary to common sense, demon decides to kill Maggie to "save" his half-brother from of "emotional weaknesses". When Hunter breaks out a fight in the manor's backyard, Parker exposes his powers and identity in front of the sisters in attempt to protect them.
Between them there is a turning point when Hunter begins to think that his half-brother wanted to kill him, and Parker did nothing to dissuade him from this thought. Demon severely beats his hybrid brother and since then allows himself all sorts of harsh insults against him. However, he suffered because of S'Arcana crows and had to escape.
Hunter later returns to settle the score with the Vera sisters and Harry, but Parker comes to their rescue and tries to banish Hunter to Tartarus. However, he grows weaker with each attempt and the sisters help out. They succeed in banishing Hunter, but in the end he has time say to Parker, that he will pay for this betrayal.
Brothers don't have direct interaction, but within a week after the events of spoiled Christmas, Parker kept deceiving their dad about the real whereabouts of his brother (he said that Hunter had stolen the amulet and now doesn't want to be found). Parker was hiding the truth because he was afraid to bring the wrath of Alastor upon himself and his mother.
And at the moment, it is unknown whether Parker feels the slightest remorse due to the fact that Hunter is in Tartarus because of his fault.
Hunter is broken out of Tartarus by Charity, and proceeds to manipulate Parker into thinking he killed his mother when he shapeshift into her and acted dead when Parker's powers went haywire. After Parker left in distress, Hunter killed his mother who he had tied up in a closet.
Hunter later shapeshifted in Maggie in order to make Parker think that she had turned on him and that he had nobody left, so that he would participate in their father's plan to raise the Source.
- Hunter called his brother by the nickname "Park," when he was not mad at him.
- The fans attributed to the brothers the surname "Caine," but it was not made official until Deconstructing Harry.
- It is currently unknown what their age difference is.