Their pronouns change over the years.
They're going by he/him this time around, mostly because they present as males anyway, but they're pretty loose with labels.
Blaine has taken to bow ties and short-sleeved collared shirts. They wrap around his arms and emphasize his muscles, and bow ties make his neck feel like a present, which is a bit ironic when he thinks about it.
Kurt has taken to structured outerwear and scarves. They cut a sharp figure on him and make him feel sleek and untouchable. And to most people he is. Blaine has seen people fawn over him and stare from afar for decades, and it's become more overt now. But they can't touch him, no. He's Blaine's.
They meet during the 18th century.
Blaine wears billowy clothing with lace and silk. Her curls are long, and her eyes somehow retain a bit of kindness. Living in Europe has been a rough transition. They are less free about their ideas of gender, so Blaine has to make do. And if that means a more feminine look, then so be it.
She's walking down the street late at night when she hears a muffled scream from one of the alleyways up ahead. She runs over to the corner and peers in to see a man slumped on the floor. A taller figure stands over him and places bottles of ale around him. Blaine sees a faint mark on his neck that slowly starts to heal, and she walks over. She senses when the other person tenses and turns around to face her, but she flashes her fangs and smiles.
"Good evening. My name's Blaine."
And that's how their eternity together begins.
Blaine learns that Kurt has lived here since the beginning.
They spent the rest of that evening walking by the pier and exchanging stories of their lives up until that point. When the sun begins to rise, they part ways and make promises to meet up that night and every night after that. And that's what they do.
They become Kurt-and-Blaine.
They spend every evening they have together. To maintain appearances, Kurt courts Blaine, but it isn't anything they both don't want. There are subtle glances and touches, flowers exchanged in the eyes of the public. In private, they feed together and take care of one another.
Kurt learns about Blaine's gender fluidity, learns that while she presents as a woman, she doesn't always feel like that. Sometimes she feels like a man, and other times she finds herself sliding on a spectrum that blurs the lines altogether.
Blaine learns about Kurt's gender nonconformity. They said, "Clothing has no gender," and they've experimented throughout the years. They've settled on presenting mostly male, but that doesn't mean they don't try new things every now and then.
They find comfort in one another, and their complete understanding of each other makes it all the better.
It's the beginning of a love Blaine never thought she could have.
They save up money over the years. They get good at reinventing themselves and moving every now and then to keep suspicions low. They survive the wars and the famines and every conflict that arises.
They never join a coven, but every one of them knows about Kurt and Blaine. They know that they're powerful both together and apart and that if you went after one of them, the other would twist your head off an instant and burn you to hell. They are kind to those who deserve it, and they welcome everyone with open arms, but there is still a bubble that exists around them. They gravitate towards each other and make everyone feel like they're lucky to be even looking in at how they live.
They may be alone, but they're together and that makes up for all of it.
They move to America in the 20th century and lead a more conservative lifestyle in the city for a few years. They suffer through the insults and the aggression of people who don't understand them, but it's fine. If they get their dinner from the man who calls them fags on their way to work, then well, it's what they have to do.
They retreat to a small town by the ocean on the east coast in the sixties. The older folks are less accepting, but they do their best to establish strong relationships with the people who lives there. When the older folks die, Kurt and Blaine work to create a welcoming environment that lets them and others live in peace. They walk away from it after a couple decades, but when they manage to visit, they notice the place they've built has only continued to flourish.
A little over a decade into the 21st century, they get married.
It's not the first time, but it's the first time in America and they use it as a chance to celebrate their lives up until this point. They say their vows in a forest on the west coast and share kisses in suits of Kurt's design. Blaine's got billowy sleeves and lace across the front, and Kurt's got a cape that leads into a train. It's reminiscent of when they first met, and Blaine has his heart in his eyes when he kisses Kurt every time that night.
They decide to settle back in the city. The world still isn't the most accepting, but it is leaps and bounds beyond what it was. They spend their summers back in the small town they built together, but they work in the city. Blaine composes and Kurt designs, and they live quiet lives. They do their best to contribute to the world they have seen change so much around them and hope to push it to change for the better. It's the least they can do.
They've spent so many centuries together, and they haven't even come close to becoming tired of one another. They go out during nights to dance and sing the night away, and they'll meet up for lunches or walks around the park when their breaks line up.
They are still Kurt-and-Blaine to everyone who knows them, and Blaine likes to think they'll continue to be.
After all, they have an eternity to spend together.