Summary
When she was first introduced as “Krista Lenz”, Historia was made to embody the ideal “waifu”; being selfless, grateful, and even breaking up fights, she quickly earned the favor of her male peers, especially Reiner. Come the end ofAttack on TItan’ssecond season, this proves to be a ruse, as it’s revealed that Historia had beenputting on an actin order to please others - as observed by Ymir.
This didn’t go unnoticed by Eren either, who previously told her to drop the act and just be herself. Eventually, after Ymir’s death, Historia would come to live for herself. Though many fans speculated about a blossoming romance between the two, their relationship is a lot more complicated.

Two Sides of the Same Coin
In the beginning, Eren and Historia didn’t have a lot of interaction until Eren was abducted by Rod Reiss in season 3. From there,he learns that it was his father who killed Historia’s family, and out of guilt, asks her to go through with turning into a Titan and eating him, as instructed by her father. Remembering her promise to Ymir to live for herself, she rebels and decides to free Eren. Despite his initial protests, she reminds him that it’s his own life that he dictates, and shouldn’t play the “nice guy” out of guilt, similar to what he told her.
Afterward, Historia takes up the throne as Queen thanks to the support of the Survey Corps and earns the respect of her peers, especially Eren. Given her royal blood and Eren’s position as the main character, many speculated that hewould come to have the same relationship as Grisha did with Dina, insinuating that he was going to follow in the footsteps of his father.

The Pregnancy Subplot
In season 4, to combat Zeke’s plan for Paradis, Historia agrees to offer herself up as the new vessel for the Beast Titan, and eat Zeke. Though that would fix the threat, it would involve shortening Historia’s lifespan and continuing the cursed legacy of the royal family. Eren,having already seen the future and seeking to avoid further losses, opposes this idea.
Yelena meets Eren in secret to inform him of Marely’s planned attack on Paradis and Historia’s role. With Historia’s welfare in mind,he approaches her and tells her his plan for the Rumblingalong with the information Yelena provided him. Unsurprisingly, Historia is distraught about this knowledge, but with no other choice, she suggests that she have a child, to stall the initial plan of her eating Zeke.

After this conversation, both in the manga and anime,viewers were left wondering if Eren was the father and theorized that he had a secret relationship with her. This sparked debate among fan communities about the scene. Some even went as far as to analyze a panel fromAttack on School Castes(a short comic taking place in an alternate universe) in a previous volume, to imply that he was directly involved in Historia’s pregnancy.
In said panel, Eren apologizes to Historia over a rumor she made up, so she doesn’t face repercussions for lying. While some users believed Eren’s gesture correlated to impregnating her (protecting her), others theorized that because of Eren’s lie,background characters assumed he was involved, similarly to the Military Polices' speculation on who told Historia about their plans. SinceSchool Castesuses opposing parallel events to the main timeline, it was foreshadowing that it was merely Eren telling her the truth; as opposed to him telling a lie.

However, the “Eren is the father” theory had already been debunked in a previous chapterwhen it’s confirmed that Historia already had someone in mind- that was a man who bullied her in her childhood (dubbed “The Farmer”) but sought to make amends. Despite the reveal, fans continued to speculate that it was a red herring, though other panels and series of events indicated that it was indeed her choice to approach him. After the manga ended, there were online discussions that Eren was purposely set up to be a candidate, so the reveal of him being in love with Mikasa came as a larger surprise.
Other characters (including Levi) were suspicious of the timing of her pregnancy, being that she “just so happened” to “fall in love” right before the plan to capture Zeke was enacted. Furthermore, to buy herself more time, she had informed Levi that she wasn’t due for months. Come the conclusion ofAttack on Titan, the official guidebook confirmed The Farmer as the biological father, with her child’sappearance lacking Eren’s features in the anime. It’s safe to say, for the sake of retaining audience interest, having Eren as a red herring for Historia’s pregnancy is justified - but some audiences felt it was underwhelming. While a portion of the fanbase believed that Historia’s character was tossed aside, others admired the simplicity of it - the father of her child was irrelevant, it was always about her and her decisions.

Were They or Weren’t They?
An early draft of Isayama’s shows Eren saving Historia in chapter 4, and later interviews with the editorial team suggested that Historia was an important asset to Eren’s character development. Side content parodied a relationship between the two, so fans took that as confirmation that it was intended for the two to be canon. However, relationships and attractions between characters (such as Jean towards Annie inAttack on Titan: Junior High) are not uncommon in side material. Additionally, throughout the series, Historia and Eren’s love interest, Mikasa are close friends. In episode 10 of season 4, the former teases the latter about her feelings for Eren.
Despite their close relationship, Eren and Historia did in fact divert from the footsteps of their parents, making their own independent choices.In the end, Eren achieved temporary peacefor his friends, and Historia was able to have a family of her own - birthing the first child into a world free of Titans.