First, you need to understand their characters well. Luke is complex, with his initial good intentions that gradually get corrupted. Thalia is strong - willed and protective. Start with a clear idea, like exploring their past friendship. For example, you could write about a time when they went on a quest together. Then, build the plot around their relationship, adding in elements from the Percy Jackson universe.
There's a fanfiction called 'Luke and Thalia: The Forgotten Days'. It's set in their early days at Camp Half - Blood. It's interesting as it explores their initial interactions and how they became friends. It also gives a new perspective on their personalities. You can find it on some popular fanfiction websites.
Luke Castellan once fell in love with a girl from the same camp. They met during a training session. He was instantly attracted to her bravery. They started to secretly meet in the forest, sharing their dreams and fears. But as Luke's path started to turn darker, their love was put to the test. Eventually, she couldn't follow him into his wrongdoings and they had to part ways.
Yes, there are quite a few out there. Some fanfiction platforms like Archive of Our Own (AO3) have a wide range of such stories. You can search using the tags related to Percy Jackson, Luke Castellan, and the gay relationship to find ones that suit your taste.
There's also 'Percy and Luke: A Different Path'. This fanfiction takes a different approach. It imagines if Luke had made different choices early on. Percy plays a key role in guiding Luke towards a better path, and their relationship blossoms as they both learn and grow together.
One common theme is the struggle against fate. Since they are in a rather complex situation in the original story, in yaoi fanfiction, they often have to fight against the expectations of the demigod world to be together.
One possible plotline could be that they are long - time friends who gradually develop feelings for each other and the kiss is a culmination of that slow - burn romance. For example, they might go through various adventures together, and during a particularly emotional or dangerous moment, they share a kiss.
One great 'Percy Jackson Thalia Grace' fanfiction is 'The Lost Sibling'. It delves into a scenario where Thalia and Percy discover they are long - lost siblings. The author does an amazing job of portraying their initial shock and then the gradual building of a strong bond. It has some really exciting battle scenes against mythical creatures too.
Luke might have fallen in love with a kind - hearted healer in the camp. They bonded over his injuries from battles. She would tend to his wounds and they'd talk for hours. But when Luke decided to side with the Titans, she was heartbroken. She pleaded with him to change his mind but he wouldn't listen. Their love was shattered by his choices.
AO3 (Archive of Our Own) is a great place to start. It has a large collection of fanfiction, and you can easily search for stories about Percy and Luke with the gay relationship tag.