There are indeed some. One way to find them is to search on specific fanfic communities dedicated to Supernatural. These fanfics often explore different aspects of Sam and Dean's relationship. They might rewrite certain scenes from the show with a gay subtext or create entirely new storylines based on the idea of them having a romantic relationship. Just keep in mind that the quality can vary greatly from one fanfic to another.
The theme of family legacy is quite prevalent. Since they come from a family of hunters, many fanfictions explore how this family history affects their actions and decisions. Also, the theme of growing up in a tough environment is common. They face a lot of hardships at a young age, and fanfictions often depict how they cope with it and become stronger.
Since I don't actively engage with this type of fanfiction, I can't say for sure. But generally in fanfiction, themes might include the intense emotional connection between the characters, perhaps with a romantic or sexual undertone.
One common theme is the exploration of their deep emotional bond in a romantic context. Since they already have a strong brotherly bond in the original show, fanfictions often build on that to create a more intimate, romantic relationship.
The Archive of Our Own (AO3) is a great place to start. It has a large collection of Supernatural fanfics, including those that explore a gay relationship between Sam and Dean. The site has a good search function that allows you to filter by tags related to the characters and the type of relationship you're interested in.
There are some fanfiction communities like FanFiction.net as well. However, the quantity of specifically gay Sam and Dean Winchester fanfictions might be less compared to AO3. But it's still worth a look. You might have to dig a bit deeper by using specific tags related to their relationship in a gay context while searching.
One great young Sam and Dean Winchester fanfiction is 'The Brothers' Bond'. It beautifully captures their early adventures and the development of their relationship. The story is full of action and heart - warming moments between the two.
I'm not really into that type of fanfiction. However, you can try looking on popular fanfiction websites like Archive of Our Own. They usually have a wide variety of fanfictions related to Sam and Dean Winchester, and you might be able to find some that suit your taste.
Harry would probably have a complex relationship with Sam and Dean. Since they are his half - brothers in this fanfic, there would be a sense of family loyalty. Dean might be a bit overprotective at first, seeing Harry as the younger brother he needs to keep safe. Sam, on the other hand, would likely be interested in Harry's magical knowledge and how it could be applied to their hunting.
Dean Winchester once met a girl in a small town. She was a librarian. Their eyes met across the dusty bookshelves. He was drawn to her kindness and intelligence. They started to talk about old books and soon, love began to blossom. They went on drives together, sharing stories of their pasts. Dean found in her a sense of peace he hadn't known before.