In some fanfictions, Naruto's mother might be a character related to the Uchiha clan in a unique way. It could be someone who was secretly in love with an Uchiha and had Naruto as a result. Maybe she was a long - lost relative of the Uchiha who was trying to protect the clan's secrets through Naruto.
Maybe it could be an existing female character from the Naruto series who steps into a motherly role for Naruto. For instance, Tsunade. She already has a sort of protective and guiding role in Naruto's life, and in the fanfiction, this could be developed further into a full - fledged motherly relationship.
One possible plot could be exploring her relationship with the Uchiha clan before Naruto was born. Maybe she was involved in some sort of secret mission within the clan. Since she was Naruto's mother, her actions might have had an impact on Naruto's future in some hidden way.
Maybe it's an adopted child. Naruto, with his big heart, could have taken in an orphan from one of the village's tragedies. This would give him the role of a single mother in a very unique way as he tries to instill his values and ninja skills in the child.
It could be Hinata. Since they got married in the original series, it would be a natural choice for her to be the mother in the fanfiction.
One possible plotline could be that Naruto's mother, being an Uchiha, passes on some unique Uchiha abilities to Naruto. Maybe he has an easier time learning certain jutsus related to the Sharingan, even without actually having the Sharingan himself. For example, he could have a natural affinity for fire - style jutsus which are common among the Uchiha.
One common plotline could be the mother trying to hide Naruto's connection to the Uchiha from the rest of the village. Since the Uchiha had a somewhat controversial history in Konoha, she might be worried about Naruto being ostracized. Another plotline could be Naruto inheriting some sort of special Uchiha - related power from his mother, which he then has to discover and master as he grows up.
It could be Sasuke's sister, if there was one in the fanfiction world. She might share some of Sasuke's traits but also have her own unique personality that attracts Naruto.
Her Uchiha heritage could give Naruto a stronger connection to the Sharingan. Even if he doesn't directly inherit it in the traditional sense, it might influence his perception and ability to deal with Sharingan - related threats. For example, he could have an instinctive understanding of how to counter certain Sharingan techniques.
Obviously, Hinata's mother would be one of the main characters. Hinata's father would likely be another important character as their relationship is crucial to Hinata's family background. Also, young Hinata herself could be a main character in flashback scenes, showing how her mother influenced her in her formative years.
It could be a completely new character. Maybe Naruto met her during his travels, and for some reason, she had to entrust the baby to Naruto. This could be due to her being in danger or having some kind of mission that made it impossible for her to take care of the baby herself.