A very loving and exciting one. James and Sirius were both full of life. They would likely fill Harry's childhood with adventures and magic lessons. There would be a lot of laughter and pranks around the house.
The family environment would be unique. Since James and Sirius were both Gryffindors, there would be a strong Gryffindor influence. Harry would be surrounded by stories of their time at Hogwarts. They would teach Harry how to use magic creatively and how to handle difficult situations. There would be a lot of magical artifacts and books around the house as both were interested in magic. And they would support Harry unconditionally, creating a nurturing environment for him to grow into a powerful wizard.
It could be a crossover fanfiction where characters from Doctor Who interact with those from Harry Potter, especially Sirius and James. Maybe they travel through time and space together or face some magical adventure.
Well, it completely flips the story on its head. In the original, James was Harry's father and Sirius was his godfather. But if they are both his parents in fanfiction, it means a different family structure. Harry might grow up with a more united front of his two dads, perhaps having a different set of values instilled in him. Also, the relationship with the wizarding world might be different as they both have their own connections and reputations within it.
Adventure is also a big theme. Just like Harry had his own adventures at Hogwarts, fanfictions often have James Sirius getting into various escapades and Harry either being involved directly or guiding him from the sidelines. It gives a sense of passing on the torch of bravery.
Sirius could help Harry cope by sharing his own experiences of being an outcast in his family. He could tell Harry that just because his parents did this horrible thing, it doesn't mean he's unlovable. Sirius could also introduce Harry to his friends in the wizarding world, like Remus, who could also offer support and friendship.
At first, they might be just friendly acquaintances. As they grow, they could become best friends. Fleur's Veela charm might initially make Harry a bit shy around her, but as they get to know each other better, he sees past that. Later, as teenagers, they could develop a romantic relationship. Fleur's elegance and Harry's heroism could attract them to each other.
Well, Harry would likely be much more confident at Hogwarts. With his parents alive, he would grow up in a loving and magical home environment. This would translate into his school life. He would probably be more social and make friends more easily. He might also be less likely to get into dangerous situations with Voldemort. His parents could even be involved in the school in some way, like teaching a special class or being on the board of governors. This would give Harry a certain amount of privilege and protection that he didn't have in the original story.
Maybe James Sirius Potter did something really reckless. For example, he might have put himself in danger while exploring some forbidden areas in Hogwarts. Harry, having gone through a lot of dangerous situations himself, would be worried and yell out of fear and frustration.
Family is a major theme, of course. But also, there's the theme of identity. Harry would have a different identity compared to the original story. He might struggle with how he fits into the wizarding world now that his parentage has changed. And then there's the theme of friendship. His relationships with Ron and Hermione could be altered, as he comes from a different family background, and this can lead to different interactions and storylines.
Yes, there are some. You can start by looking on fanfiction websites like Archive of Our Own. There are often unique takes on this concept where the author explores how Harry's life would be different if he were the son of Sirius and James. Some stories might focus on the family dynamics, with Sirius and James being alive and raising Harry in a very different magical world from the original story.
Well, you could imagine a time-travel adventure where Sirius and James get pulled into the Doctor Who universe and have to face off against some alien threats.