|“||Dang, sis. That was harsh.||”|
It was revealed in Fade Into You that there's a 18 year age gap between them. Different from the rest of his family, Kai was born with no magical power of his own but was gifted with the ability to absorb the power of others. Based on the tradition of the coven, only a set of twins would become leaders, hence their name "Gemini."
On the other hand, at the age of 22, the twins have to merge power. The stronger one would absorb the power of the weaker, who would die as the result. Realizing Kai's disability, the Parker family kept having children until another set of twins were born. Liv and her twin brother Luke entered their lives as the 7th and 8th children of the family and the 2nd set of twins.
Kai killed 4 out of 7 of his siblings, attempted to murder the twins, but failed because Jo protected them.
Throughout The Vampire Diaries Series
In I Alone, Kai reaches his destination, where Liv is. He asks Liv for a drink, but she believes he's too young. When he shows her his ID, she still refuses him a drink. He then reveals that he is the brother that tried to kill her and Luke. Liv backs away, but Kai takes some of her magic. As Liv attempts to escape, she runs upstairs and Kai follows. Before he can kill her, Tyler pushes him over the railing and Kai flees.In Christmas Through Your Eyes, Kai is seen at the cemetery with Liv and Luke. It is revealed that, in order to escape the Merge, Liv and Luke located Jo's Knife (on this plane) and Kai wants to "reunite" Jo with her powers through it. Later Kai gives Liv the knife and tells her that she had better find a way to put their sister's magic within the dagger or he will use it to slit her throat and then leaves to get a bandage. Kai returns, overhearing Liv pep-talking Jo, informing her that she has come a long way without magic and she could become more with it. Kai then grabs Liv's shoulders, absorbing her magic and knocking her to the ground as it brings her pain. Kai then begins to give her an aneurism and asks Jo if it would be funny if he killed Liv with her own magic and verbally ponders whether that would be funny or sad as he apparently gets his emotions mixed up. As he goes on hurting Liv, he asks Jo what is the spell for fire again and he correctly guesses it is incendia.
In The Day I Tried To Live, Liv tries to kill Kai in revenge for the death of Luke. However she is eventually stopped due to Damon's interference with her magic and Tyler verifies that he brought her home. Later, Kai tries to bring himself to kill Liv, but he can not because of the parts of Luke's personality which he received after the merge.
- Kai: "No bourbon. I’m secure enough in my masculinity. Vodka’s boring, rum’s too tropical. Oh, tequila. You do not want to see me on tequila. What about gin? Is that weird?"
- Liv: "Not unless you’re 50."
- Liv: "Stay the hell away from me."
- Kai: "You were always so bad at hide-and-seek. I mean, you were 4, but still, find a better hiding spot."
- -- I Alone
- Kai: "I'm going to find a bandage while you figure out how to put the magic in this knife into our sister. Preferably by the time I get back so I don't have to dull it by slitting your throat."
- Liv: Then I want to kill Kai.