A really interesting plot for 'kakashi and naruto family fanfiction' could be that Kakashi accidentally stumbles upon a secret power within Naruto's family that has been dormant for generations. He then helps them unlock and control this power. Along the way, they form a stronger bond as a family. And as Kakashi is involved, he also rediscovers some of his own values and beliefs through this process.
A possible plot is that Naruto discovers a hidden power within Kakashi that even Kakashi was unaware of. This discovery leads them on a journey to explore the origin of this power. Maybe it's related to an ancient clan. As they dig deeper, their relationship grows stronger and they face many challenges together from enemies who also want this power.
One idea could be a story where young Kakashi has to protect a young Naruto from a group of rogue ninjas. It could show Kakashi's early skills and Naruto's innocent yet determined nature.
One plot idea could be that the female Naruto has a special training session with Kakashi. During this, she discovers a new jutsu that Kakashi has been secretly working on. He decides to teach it to her because he sees her potential. This new jutsu then becomes crucial in a future battle against a powerful enemy.
One idea could be that little Naruto gets lost in the forest and Kakashi has to find him. Along the way, Kakashi discovers Naruto's secret hiding place filled with his dreams and wishes written on little scrolls.
One interesting plot idea could be Kakashi getting transported into a different Naruto timeline where all the villains have joined forces. He'd have to use his Sharingan and vast combat experience to survive and find a way to stop them. Another could be Naruto and Kakashi swapping bodies for a while. This would lead to some comical situations as Naruto tries to act like Kakashi and vice versa. Also, a crossover where Kakashi is sent to a parallel universe where Naruto doesn't exist, and he has to train a new group of ninja in the ways of Konoha.
One idea is that an enemy targets Kakashi's Sharingan and Naruto has to protect it. Along the way, Naruto learns more about the Sharingan's capabilities and how to use it against the enemy. This would be a great opportunity for Naruto to grow as a ninja and for their friendship to deepen.
One idea could be that Female Kakashi is assigned to train Naruto in a special jutsu. During their training, they discover a long - forgotten scroll that contains a powerful technique. As they work together to master it, they face challenges from other ninja who want the scroll for themselves.
Another plot could involve Naruto training a group of new genin in the same strict yet effective way that Kakashi trained him and his friends. Along the way, he discovers that one of the genin has a hidden power similar to his own, and they bond over their shared experiences of being different. This story could show Naruto's growth as a teacher and as a ninja who is now emulating Kakashi.
One interesting plot idea could be Kakashi traveling back in time to before the Uchiha massacre. He could try to prevent it, which would completely change the future of the Naruto world. Maybe he'd have to face off against Danzo and his schemes early on.
Perhaps a story where Kakashi's past Anbu experiences resurface during a mission with Naruto in the Anbu. They have to deal with an old enemy that Kakashi thought was long gone, and Naruto helps him come to terms with his past traumas.