Jokes -Kol Mikaelson-

"Why are movie stars so cool?"She asked Kol, who was unamused by the jokes that she had everyday.
"I don't know, Katara. Why?"Kol deadpanned, and the girl in front of him smiled, and his heart fluttered.
"Because they have so many fans!"
"You're jokes keep getting worse, Kat."
"You love my jokes!"
"Keep telling yourself that, Kat.

Back from before Kol became a vampire, he knew Kat, loved her even. Then he got turned and his life changed forever, and so not wanting to lose her, he had her turned by his mother. She let him, now she was an original. Of course at the time she was in love with Klaus, who loved Tatia.
Kat was one of the original vampires, he made sure of that. And when Kol was daggered, she was.
Ten years before Kol was woken up again, she runs from the Mikaelson family, Klaus had undaggered her, needing advice, and she gave it to him with the condition that she can go, the story being that she ran.
Kol, of course, was heart broken when he found out. He wanted to search for her, and he didn't have to. They were all in the same town of Mystic Falls.