If you were a jet, you hated the sharks, and the other way around.
Kurt was raised into a shark gang, and had therefore learned not to interract with the wrong people.
But when he met Blaine Anderson, a former jet member, he couldn't resist.
Blaine was gorgeous, sweet. Tanned, a great singer and had a fantastic sense of fashion.
They had met at the annual Ballroom Dance, and had fallen into a heated secret relationship.
When Blaine had asked Kurt to meet him at Kurts workplace, he had immidiately said; "Yes, i'd love that", and Blaine had kissed him like it was their last kiss.
They had gotten married that night, with mannequins as guests, and rings made out of candy paper, but to them it was the ideal wedding ceremony.
And then hell broke loose. Blaine had experienced, not only his best friend, and Jet leader, Mike Chang die, when he was stabbed to death, but also Kurts older brother and Shark leader Finn Hudson. He had told Kurt that night, and Kurt believed he didn't do it, and afterwards they made love. Of course, when Kurts sister in law and recent widow, Rachel Berry had found out, she began yelling at him for marrying an enemy.
After half a year of fighting, Blaine was shut to death. He lay there peacefully dying in Kurts arms, while Kurt yelled curse words at the gang members, for not thinking about the consequences.
Kurt kissed his forehead and watched as the members left the playground.
