In some fanfictions, it could be Sirius Black. Some fans like to imagine that Sirius had a deeper connection to James Potter's family than just being best friends. They might create a scenario where there was some sort of magic or prophecy involved that made Sirius more than just Harry's godfather, but his actual father in this alternate story line.
Maybe Ron Weasley. Imagine a fanfiction where Ron, after getting married, has triplets. Given his humorous and sometimes clumsy nature, it would be really fun to see how he and his wife deal with three little ones. He could pass on his love for food and his loyalty to his children in a really endearing way.
One theory is that Remus Lupin could be Harry's real father. Lupin was a close friend of James and Lily. In fanfiction, writers might explore the idea that there was something more between Lupin and Lily. Maybe Lupin's werewolf nature was somehow involved in a magical way that led to Harry's conception, creating a whole new backstory for Harry that is very different from the original story.
It could be Sirius Black. Maybe there was some misinformation that made Harry believe Sirius was his father for a while, but then it turns out he isn't. After all, Sirius was very close to Harry and had a father - like relationship with him in some ways.
Yes, there are likely to be such fanfictions out there. The 'Harry Potter' fandom is vast and full of creative interpretations. Some fans like to create unique family relationships in their fan - made stories.
I'm not sure if there is such a specific fanfiction. There are countless fanfictions out there, and while some might come up with really wild and creative ideas like this, it's not a common or well - known one that I'm immediately aware of.
One possible scenario in a fanfiction of Harry Potter's father and a Murkrow could be that the Murkrow is actually a transformed Animagus. James Potter might initially be suspicious of it but then realize it's an ally in some sort of secret mission against the Dark Arts. Since James was part of the Marauders, he was always into adventures, and this could be one such adventure involving a strange creature like the Murkrow.
There could be old friends from their school days. For instance, a classmate who knew some deep secrets about them. Maybe this friend was also in the same secret club or society that his parents were part of, and after their deaths, this friend tried to keep an eye on Harry from the shadows.
One potential character could be Seamus Finnigan. He has a bit of a fiery personality, and it would be interesting to see how he would handle being a teenage father. Maybe he accidentally gets into a situation where he has to take on this role.