See: Eris siblings' father and Eris siblings' mother.
Background[]
The parents to Lucile Eris, Ferris Eris and Iris Eris appear only in the "4 years ago" sequence at the beginning of episode 16. Their given names are never revealed.
Involvement in Plot[]
From a young age, Ferris was trained in fighting by her mother and father, both of whom considered her a dissappointment not worthy to bear the noble name of Eris. Ferris' mother and father were siblings, who married each other in order to keep the blood of the Eris house and line, which they consider to be of utmost importance above all else, pure. (Ferris and Lucile were also originally intended to marry each other as well to continue the Eris line.) Because both Ferris and Iris were such "failures", her mother and father decided together that she was not worthy to continue the Eris family line. Their plan was that, instead, her father would rape her and hopefully she would then fall pregnant and give birth, so that there would still be a chance of producing a child worthy to carry on the Eris name and household. However, while she was pinning Ferris to the ground, Lucile murdered his mother, stating that "my dear younger sister is not meant to be soiled by your filthy hands". Lucile also kills their father soon afterwards, thus freeing Ferris from her torment and, at the same time, achieving his current position as Head of the House of Eris.
Quoted Passages[]
*quoted from Densetsu no Yusha no Densetsu: Volume 1
“The Eris clan.
This family was a famous clan that was in charge of protecting the king of the Roland Empire.
It was a noble clan with extremely great power.
It was also known as the swordsmen clan.
This clan’s mission was simply to protect the king, and never to take part in battles. Thus, very few people knew its power. However…
They were extremely famous amongst some of the nobles.
Everyone knew that that clan was the strongest.
They had a large dojo inside the city, and amongst some famous nobles, heading to the Eris’ clan dojo was like proof of being famous.
Only a small group of people could enter and exit the dojo, and those were nobles that were highly respected…”
*quoted from Densetsu no Yusha no Densetsu: Volume 3
Sion’s Thoughts: To be more accurate, it wasn’t scary, but it was on the level that it was troublesome… Iris and Ferris’s brother, part of the family of swords, protector of generations of the kings of Roland—the Head of the Eris family.
But protector was not very accurate. In reality, he could even take the king’s life as the country’s gears, a presence to protect the country.
If Lucile thought that Sion’s ability to be king was lacking, then he would kill him.
And no one could stop him.
He was truly a monster…
But his younger sisters, Ferris and Iris had their adorable sides… But because they had been receiving abnormal training from the Eris Family since they were young, they lacked a common knowledge…
She had never seen anyone cry, this girl had said this. No matter how uncomfortable or sad, crying wasn’t allowed. No, they didn’t even know about the existence of feelings. The Eris Family was a place like this.
According to what Ferris said, if they had not grown to a certain standard, they wouldn’t even know that there were other people living beyond their family walls…
Although Iris didn’t seem as bad as Ferris, but…
*Quoted from OKYD Vol. 5 Chapter 1
“The sword family, as they were called, in the frightening Eris household—day and night, it was always dark.
Power was the name of the monster that had taken hold of this house, the sole darkness that continued to drive them insane.
If one wasn’t strong, they weren’t allowed to live.
If one didn't possess enough power so as to not shame the Eris house's name, they weren’t allowed to live.”
“The sword family, as they were called, were renowned for their swordsmanship skills, and so as not to dilute their blood, they married their relatives—and continued produce children with the same face, the same ability.”
{Based on Baka-Tsuki Translations}