In fanfiction, when Naruto meets his father, he might first be in shock. His father could impart some long - lost family jutsu knowledge to him. Maybe he would also share stories about Naruto's mother that Naruto has never heard before.
Well, it could be a very emotional encounter. Naruto would be able to see his parents in their prime. His father, Minato, might give him advice on how to better handle his role as a Jinchuriki. His mother, Kushina, could cook for him, just like she always wanted to do for her son. They could also talk about the future of the Hidden Leaf Village and Naruto's part in it.
One common theme is identity crisis. Since there's an imposter, Naruto or other characters often face questions about who they really are. Another theme is trust. The villagers and Naruto's friends have to figure out who to trust when there's an imposter around.
His brother could be an unknown Uzumaki. Since Naruto is from the Uzumaki clan, it would make sense for his brother to be from the same clan. Maybe he was hidden away for some reason, like to protect him from the same threats that Naruto faced as a child.
She could be an Uzumaki. Since Naruto is from the Uzumaki clan, it would make sense for his grandmother to be part of this powerful and mysterious clan. Maybe she has some unique abilities related to the Uzumaki's sealing techniques.
He could be a powerful and respected shinobi from the Uzumaki clan. Given the Uzumaki's reputation for strong chakra and unique abilities, Naruto's grandfather might have been a key figure in the clan's history.