Perhaps a family of magical scholars. They would expose Harry to all kinds of ancient magic texts and theories. This would make Harry not only a better wizard in terms of practical magic but also in understanding the deeper roots of magic. They could be the ones to finally unlock the full potential of Harry's magic, which was stunted by his difficult upbringing at the Dursleys.
It could be an old pure - blood family that has been in the background in the original series. Maybe the Blacks who have some complex family dynamics already and taking in Harry could add a whole new layer of drama.
One member could be an old, wise wizard who has been living in seclusion for years. He might have a deep knowledge of ancient magic and decides to share it with Harry. Another could be a young witch who is very talented in potions and charms. She could be like an older sister to Harry, helping him with his studies. And there could be a gruff but kind - hearted wizard who is an expert in defensive magic and teaches Harry how to protect himself.
His wife could be an original character created specifically for the fanfiction. She could be a strong - willed healer who helps Naruto when he first arrives in the new place. Their child could inherit Naruto's blond hair and blue eyes, and have a unique combination of Naruto's ninjutsu skills and the mother's healing abilities.
It could be an uncle. Maybe an uncle who was in hiding all this time because he was afraid of Voldemort. Now that Voldemort is gone, he comes out and reveals himself to Harry. He could have a lot of knowledge about the Potter family secrets and magic that he shares with Harry.
It could be the Malfoy family. Imagine Hermione being switched with a Malfoy child. Draco would be in for a huge shock when he realizes that the sister or brother he thought he had is completely different. And Hermione would have to deal with Lucius and Narcissa's pure - blood mania.
A magical tutor for Harry's kids could be an interesting addition. This tutor could have some really unique magical abilities and a mysterious past. Maybe a young witch from a far - off land who brings new spells and cultural elements of magic to the story.
They could have a son named Albus, after Albus Dumbledore. He might be a brilliant wizard with a strong sense of justice, just like his parents.
Potential members of the harem could include Nymphadora Tonks for her ability to change her appearance and her feisty nature. Parvati Patil, who is interested in divination and has her own brand of confidence. And then there's Alicia Spinnet, a talented Quidditch player. All of these characters have their own qualities that could make them interesting members of a 'harry potter badass harem' in fanfiction.
Fleur Delacour could be part of the harem. She is beautiful and confident. An OC who shows great courage and skill, perhaps in the Triwizard Tournament, could catch her eye. Then there's Cho Chang. If the OC has a sensitive side and an understanding of her past experiences, she might be interested. Also, Padma Patil. If the OC has an interest in different cultures of magic, as Padma comes from a different cultural background within the wizarding world, she could be attracted to the OC.
Black Widow could be one. She's attracted to his unique magic skills and his sense of justice. Another could be Peggy Carter. Her old - fashioned values might be charmed by Harry's chivalrous ways. And then there's Shuri. She'd be interested in Harry's magic as she is into new and different forms of technology and power.