Grandfather Arlert

Mr. Arlert was the grandfather of Armin Arlert and the father of Armin's dad. After the fall of Wall Maria, Mr. Arlert died at the hands of the Titans.

Appearance
In the anime, Mr. Arlert was an older man with a rather youthful face yet very aged hands and body. He had light brown eyes and shaggy brown hair with a beard and mustache that did not connect around his mouth. He was only ever seen wearing a tattered light brown hat, a faded beige sweater with a brown shirt over it and a green scarf, short gray pants, and shoes. Mr. Arlert is never given an appearance in the manga.

Personality
Mr. Arlert appeared to be a humble man in the anime, taking in his grandson when he was orphaned. He spoke with a calm tone and pitied Eren Yeager and Mikasa Ackerman after seeing their horrified expressions, stating that whatever they had seen must have been terrible. Mr. Arlert cared for Armin and his friends, convincing the soldiers distributing food in Wall Rose to give him extra for the children.

History
Before the fall of Wall Maria, Mr. Arlert possessed a book containing illegal information about the world beyond the Walls. He gave this book to his grandson, Armin Arlert, who showed it to his best friend Eren, kindling his desire to see the outside world.

104th Training Corps arc
During his intimidation, or "rite of passage", from Keith Shadis, Armin states him name and is insulted by the instructor for it. When Shadis asks him if his parents gave him the name Armin replies that it was given to him by his grandfather.

The Uprising arc
Lamenting over his father's theft of the Coordinate, Eren names Armin's grandfather among the many lives who could have been saved if his father did not interfere with the Reiss family.

Anime and Manga Differences
The role of Armin's grandfather is notably expanded upon in the anime.

Fall of Shiganshina arc
In the year 845, he had been taking care of Armin until the Colossus Titan's first appearance in Shiganshina District. During this time, he and his grandson were able to board a boat and escape to Wall Rose. He continued to look after Armin and his friends, getting them food and working alongside them. He stayed as a refugee in Wall Rose for a year working the fields for food, until the central government began a retrieval operation in 846 in order to take back Wall Maria. He was summoned to be a part of this mission along with two hundred fifty thousand other people, of which only a little over one hundred survived, himself not among them. He and the others that had died during the operation were recognized silently by the people for their help in alleviating the food shortage for the rest of the Wall Maria refugees. Before his leave, he gave his grandson Armin the hat he had always worn. After hearing word of his grandfather's death, Armin is seen crying as he holds his hat in his hands. As his friend Eren Yeager tells him and Mikasa Ackerman that he plans to join the Military. Armin then bravely states that he is joining too, clearly upset at the government pushing his grandfather to his death. Their friend Mikasa states that she too will join and the three go into training together the following year in 847.

Battle of Trost District arc
When Dot Pixis is giving his orders to the Garrison and Trainee soldiers to retake Trost District, he mentions the central government's attempt to retake Wall Maria four years ago. When speaking about it he directly says that it was no more than their way of dealing with being unable to feed the refugees and that by sending them outside of the Walls, they were able to survive within them. He states that all of humanity bears the weight of that sin as Armin listens in the crowd, remembering his tears and last moments with his grandfather.