Well, you could focus on the relationship between the jinchuuriki and their extended family members in the fanfiction. For instance, how does the jinchuuriki's relationship with their grandparents change when they find out about the tailed beast? Also, a plot could revolve around the family trying to help the jinchuuriki control the power of the tailed beast. They could seek out ancient scrolls or wise sages to learn techniques that would make it easier for the jinchuuriki to co - exist with the beast.
Maybe a plot where a jinchuuriki loses control of their tailed - beast and the other jinchuuriki have to find a way to calm it down without harming their comrade. This could involve a lot of emotional moments as they try to reach out to the troubled jinchuuriki.
One idea could be exploring the relationship between the Jinchuuriki and Shukaku in more depth. Maybe the Jinchuuriki tries to communicate with Shukaku in a different way than in the original series, leading to new powers or understandings. Another plot could involve the Jinchuuriki being targeted by a new group who wants to use Shukaku's power for their own evil purposes. The Jinchuuriki then has to fight not only to protect themselves but also to keep Shukaku from being misused.
One idea could be exploring the daily lives of the Jinchuuriki in the village. How they interact with each other, share their experiences of being hosts. Another could be a story about a new Jinchuuriki arriving at the village and how they struggle to fit in.
A possible plot is that the Three - Tails Jinchuuriki discovers a unique ability related to the tailed beast that no one else knew about. For example, they could find a way to use the Three - Tails' chakra to heal others in a time of great need. This could also attract unwanted attention from those who would misuse this power. They then have to protect this new - found ability while also dealing with the normal challenges of being a Jinchuuriki.
In this fanfiction, the plot could revolve around Naruto and the Jinchuuriki family being hunted by a powerful organization. They are forced to go on the run and hide in different parts of the ninja world. During this time, Naruto discovers more about their shared heritage as Jinchuuriki. They also have to deal with the internal struggles of some Jinchuuriki who are not fully accepting of their role, and Naruto has to use his leadership skills to keep them together and safe.
You could also write about Naruto's family during a time of peace. How they interact with the other families in the village, and how they pass on the values of the ninja way to the next generation. It could include family outings, training sessions that are more about bonding than combat, and the family's role in maintaining the positive atmosphere in the village.
Maybe a plot where Naruko comes from a different village and she and Naruto have to deal with the cultural differences in their family. For example, how they raise their children with different values from two different places. They might face some opposition from their respective villages at first, but they work through it for the sake of their family.
One idea could be exploring how Naruto and Sasuke's families interact in a modern AU. Maybe they are neighbors and their kids become friends, leading to some comical and heartwarming situations as the two dads, Naruto and Sasuke, try to deal with their kids' adventures.
One idea could be that Naruto discovers his family has been keeping a dark secret from him all along. Maybe they were involved in some sort of betrayal in the ninja world that affected many lives. Naruto then decides to take revenge by exposing their actions to the village. He could start by gathering evidence secretly, like old mission reports or testimonies from other ninjas who might know something.
One idea could be exploring the relationship between Naruto and the fox family in more depth. For example, how they interact on a daily basis, their traditions, and how Naruto adapts to being part of this unique family. Another could be a story where the fox family has to protect Naruto from an unknown threat, showing their loyalty and strength. Maybe also a plot where Naruto discovers a long - lost secret within the fox family that could change the entire shinobi world.