It could be an ancient sage. In Naruto lore, there are sages who have had a great influence on the world. An ancient sage could be the one who created or fathered the bijuu. Maybe he had some great power and knowledge that allowed him to bring the bijuu into existence.
Perhaps Hagoromo Otsutsuki. He is a very important figure in the Naruto universe. He was the one who first spread chakra and had a lot to do with the creation of many things. He could be the 'father of the bijuu' in this fanfiction. He had the power and the connection to the different aspects of the Naruto world that could make this concept work.
There's also a chance it could be a completely new character created just for this fanfiction. A powerful and mysterious being who has been hidden away for a long time and is now revealed as the one who is related to the bijuu as a father figure. This new character could bring in fresh plotlines and new ways to explore the relationship between the bijuu and the rest of the Naruto world.
In 'naruto father of the bijuu fanfiction', it might be about Naruto himself being seen as a father - like figure to the bijuu. Since he has a unique bond with them. He might be depicted as having more control over them or being responsible for their growth and well - being in ways that weren't shown in the original series. It could also be about someone from Naruto's past or a completely new character who has this 'father of the bijuu' role and how that changes the Naruto universe.
It could be Shukaku. Since Shukaku was one of the first bijuu introduced in the series and has a sand - based power, it would be an interesting addition to Naruto's arsenal. Naruto's positive and energetic personality could also have an impact on Shukaku's usually grumpy and solitary nature.
In 'fem bijuu are possessive of naruto fanfiction', Kurama is likely to be a very prominent fem bijuu. Given her power and the fact that she has been inside Naruto for a long time, her possessiveness can really shape the story. Additionally, Matatabi, the Two - Tailed Cat, could also be a notable fem bijuu. Her feline nature might add an interesting layer to her possessiveness towards Naruto, perhaps making her more sly and protective in a different way compared to Kurama.
Well, having two bijuu would likely make Naruto extremely powerful. He could potentially combine their unique chakra natures and abilities in combat. For example, if one bijuu has a fire - based ability and the other has a water - based one, he might be able to create new and unexpected jutsu by mixing them. Also, it would change his standing in the ninja world. People would probably be more in awe or more fearful of him, depending on their stance towards Naruto.
One possible plotline could be Naruto struggling to come to terms with his half - bijuu nature while also dealing with his relationship with the fem bijuu. Maybe there are other characters who are either afraid or in awe of his unique state, leading to various conflicts.
In many Naruto fanfictions, if Naruto has three bijuu, they could be the Nine - Tails (Kurama) which he already has in the original series, perhaps the Eight - Tails (Gyuki) as it has a connection with Naruto's world and Akatsuki's hunt for the bijuu. And another could be the Three - Tails (Isobu). However, it really depends on the specific plot and creative direction of the fanfiction.
In fanfiction, if Naruto is half - bijuu, it could mean he has enhanced physical abilities. For example, he might have greater strength and speed like a full - bijuu. His chakra reserves could also be much larger, allowing him to perform more powerful jutsu for longer periods.
The Akatsuki might also be the main antagonists. They were after the bijuu in the original story. With Naruto having two, they would surely target him. They might see it as an opportunity to gain an even greater edge in their plan to control the world.
It could be Orochimaru. He's always interested in strange and powerful forms, and Naruto's new wolf - bijuu form would be something he'd want to study or even control for his own evil purposes.
The Akatsuki could also be the main antagonists. Since they are after the bijuu, they would surely target Naruto once he has this special relationship with them. They might try more elaborate schemes to capture the bijuu from Naruto and his 'harem' of sorts.