The Reiss family (レイス家Reisu-ke?) is an influential and wealthy family living inside the Walls. While they masqueraded as a minor noble family living inside Wall Sheena, they are, in truth, the true royal family who were in possession of the Founding Titan until it was stolen by Grisha Yeager. Currently, Historia Reiss, the illegitimate daughter of the late Rod Reiss, is the ruling queen of humanity and the last known, living member. In ancient times and on the continent of Marley, the royal family is known as the Fritz family.
In ancient times the royal family was known as the Fritz family. However, towards the end of the Great Titan War, the 145th Fritz King, a Titan shifter, constructed the Walls by use of the Founding Titan. Even though he possessed the power to eliminate the Titans, he somehow viewed a world ruled by them as true peace. To accomplish this he controlled several Titans and forced them to harden their skin and encage themselves into the three Walls, Maria, Rose, and Sheena. To protect the people, he erased their memories of the outside world and the history of the Titans, although this did not affect the Ackerman family, the Asian clan, and the noble families. After this, the royal family cast aside the Fritz name and renamed themselves the Reiss family.
Some time later, King Reiss gave the Founding Titan to a successor, dying in the process. The Reiss family ruled the Walls in secret for the next 100 years by masquerading as a minor noble family living inside of Wall Sheena. The King of the Walls would be their powerless figurehead. A special ritual would be conducted each generation that allowed them to keep their power. The Reiss who possessed the Founding Titan, the predecessor would be chained hand and foot underneath the Reiss chapel. Meanwhile another Reiss, the successor, would inject themselves with a serum and transform into a mindless Titan and devour the previous Founding Titan. This would give them the power of the Founding Titan, the lost memories of mankind, and Titan shifting powers. However, this would also give them the ideology of King Fritz and make them decide to keep humanity under the Titans' rule, even if they previously had a desire to free them.
They would never reveal the reason for this, even to their own friends and families. Being bound by this will would be noticeable by the user's dark, vacant eyes, which was apparent in Uri, Frieda, and Mr. Reiss. However, the user's eyes would differentiate between dark and their normal color, the dark vacant only occurring when they acted under the First King's will or used their Titan shifting powers. The Reiss who possessed the Founding Titan would be the true king or queen of mankind for however long they possessed it, as shown by Uri and Frieda. Usually, the ceremony would be conducted if the holder was too old or unhealthy, as the Founding Titan and the memories would be lost if the user died.
One of the many Founding Titans was Mr. Reiss, the father of Rod and Uri Reiss. Uri and Rod always begged him to exterminate the Titans, but he always refused, so much so that he locked Rod behind bars for his attempts. When it came time to pass his position to a son, Uri volunteered, asking Rod to pray. After the procedure, Uri had inherited the First King's ideology, but wished to build a paradise for mankind inside the Walls, believing that the world would end in the near future. One way he did this was by stopping the persecution of the Asians and the Ackermans. Since they were being persecuted for being immune to the Founding Titan's memory manipulation, he stopped the purges after a failed assassination attempt by Kenny Ackerman, who later became a Reiss bodyguard and Uri's closest friend.
Many years later, Rod married and had five children with his wife; Urklyn, Frieda, Dirk, Florian, and Abel. He had also conceived a sixth child, a daughter with one of his maids, Alma, his mistress and confidant. When it was discovered that Alma was pregnant, he sent her away to a ranch where she gave birth to Historia. Historia had an isolated upbringing and raised to believe she was an unfortunate, unwelcome mistake, which led to her martyr complex; she wished to die in a way in which everybody would remember her fondly and not hate her for existing. She had no friends, could never leave the ranch, was constantly harassed by children around the farm and very little interactions with her mother, who only talked to her twice, both times wishing she did not exist. Her only companionship were the animals being husbanded. She, however, had one friend, Frieda, who visited her in secret and taught her to read. Frieda told her to be a lady; a girl who was kind, gentle, and thought about those around her, a girl all would love. She would often scold Historia for not doing this and would become emotional when Historia viewed her as a lady. After her visits, she would wipe Historia's memory to protect her. These memories were only accessible in dreams for some time, yet Historia would forget them when she awoke.
When Frieda was 15, she inherited the Founding Titan by devouring Uri in the Reiss succession ritual. Before she inherited the Founding Titan, she was a cheery and generous girl who would be known to go to the fields to thank the farmers for their work. However, after becoming the true queen of humanity, she began to experience bouts of depression and mania. Historia mentions how she would go on ranting about how all humans were sinners and then feel very depressed afterwards. Historia has a flashback in which she screams at Historia, horrified, when Historia mentioned she had gotten a splinter from climbing over the fence.
Days after the fall of Wall Maria in 845, the Reiss family went to the Reiss Chapel to pray. However, Grisha Yeager, a Titan shifter who lost his wife to the attack on Shiganshina, launched an attack on the Reiss family, attempting to exterminate the whole house. He fought Frieda as a Titan to the death, but Frieda was defeated due to not being able to control the Founding Titan to its full potential and was eaten by Grisha through the neck. Grisha then killed Rod's wife and the Reiss children and destroyed the Reiss Chapel, with the only survivors of the Reiss family being Rod, who fled blindly, and Historia, who was not present. Grisha then found his son Eren in a refugee camp and injected him with a Titan serum and allowed himself to be eaten, since Eren was not a Reiss, he would not be influenced by or fall under the First King's ideology; and because of Eren's desire to slaughter the Titans for keeping humanity caged and for killing his mother, he could free humanity and do what none of the Reiss members would. With Frieda's death, Rod succeeded her as the true king.
Rod attempted to go to the farm and get Historia, possibly in order to bring her up as a true heir since his true-born children were all deceased. As Kenny describes to Historia, the reason Rod sought her out was only because he needed her blood. However, the First Brigade of the Military Police beat them there, attempted to kill Historia and Alma, with Kenny Ackerman slitting Alma's throat, being sent by Rod's congress. This was because they viewed Historia, an illegitimate child, as unfit to bear the Reiss name. Rod decided on a way to keep Historia alive; she would give up her old identity, forsake any claims, and join the Survey Corps, hopefully dying by a Titan. This was seen as an acceptable alternative, and Historia was given the identity of Krista Lenz and sent to live in a refugee camp until she was old enough to enlist in the Military. In the Military, Rod sent the Church of the Walls to monitor her. Under her Krista persona, Historia was the lady Frieda wanted her to be, but also constantly sought to die in a way that would be considered a martyr. She graduated the 10th in the 104th Cadet Corps, as Ymir, her best friend, slacked off the last several weeks of training to give Historia the 10th spot so she could join the Military Police. Historia ended up joining the Survey Corps with Ymir, in a squad under the command of Nanaba.
The Reiss Family appears to be valuable to the Hometown of the shifters. Ymir, who fears being killed by them if ever captured, believes Historia is valuable enough to them in order to earn a pardon. She would also not be harmed if handed over. Indeed, Reiner Braun, a Titan shifter hailing from the Hometown, said that his goals align somewhat with Ymir's because he wants to protect her too, indicating part of his mission is to kidnap Historia and the Founding Titan. Shortly afterward, Historia is captured by Ymir, who has allied with Reiner and his partner Bertolt Hoover to capture her and Eren in exchange for a pardon, due to eating their friend and mission partner, Marcel when she was stuck in Titan form. Historia agrees to go with if it means helping Ymir, but Reiner and Bertolt are defeated by the combined efforts of the Survey Corps and Eren's newly awakened power to control nearby Titans. Ymir allies with the two shifters and the trio escape. Ymir leaves Historia behind for her own safety and a devastated Historia reluctantly returns with the Survey Corps. The reason for Ymir wanting Historia is later revealed by Djel Sannes under the interrogation of Hange Zoë and Levi Ackerman.
In the year 850, it is discovered that the Reiss family is the true royal family and Historia has a chance to claim the throne. The rebelling Survey Corps decided to overthrow the current monarchy and install Rod as King. However, if Rod does not agree to their terms, they will instead put Historia as queen. Historia refuses, but after being physically harassed by Levi, she agreed. However, before she could take the throne, Historia and Eren were captured by Rod and Kenny. Eren was bound and gagged underneath the Reiss Chapel in the same way all of the previous Founding Titans were during the succession ritual. Rod continuously attempted to persuade Historia to transform and devour Eren, even by saying that she would be able to meet Frieda again and be strong enough to kill all Titans. Historia was about to, until she learned that all the Founding Titans fell under the First King's ideology, her sister included. Historia realized that the Founding Titan destroyed Frieda's humanity and that Rod was only using her to regain the Reiss family's power. She refused to allow Rod to do this, so she smashed the Titan serum and attempted to free Eren and escape. Rod was shocked, lightly sobbing, and crawled on the floor and licked the evaporating Titan serum, deciding to devour Eren himself. He called to his father, his brother, and his daughter, saying that he was going to be with them again. This, however, transformed him into the largest Titan in existence, a 120 meter Abnormal Titan and destroyed the Reiss Chapel. With Rod being a mindless Titan, he began to crawl towards Orvud District. The Garrison and Survey Corps led an attack on him, using explosives to blow his hands and head off. They then attempted to cut the nape of his neck, of his actual body before he could regenerate, with Historia herself delivering the final blow.
After this, Historia took the throne as queen. Historia, however, let the Scouts do much of the ruling for her, preferring to run an orphanage ranch in Wall Sheena. The orphanage is composed of all of the children orphaned in the Walls by the Titans and in the Underground Districts. She does, however, sanction the operation to reclaim Wall Maria.
The Reiss family is one of three notable bloodlines mentioned in the manga, the other two being the Ackerman family and the Asian clan. The Fritz family is also of great importance, though their bloodline is identical to the Reiss family.