It is later revealed that Kenny was Levi's uncle, who took care of the latter after his mother, Kuchel Ackerman died. After teaching Levi how to fight, he abandoned him feeling that he could not be a good parent to Levi.
Kuchel Ackermann (クシェル・アッカーマン Kusheru Akkāman?) was the younger sister of Kenny Ackermann and the mother of Levi Ackermann. She worked as a prostitute in the Underground.
Levi is the son of Kuchel Ackerman, sister of Kenny Ackerman. Their grandfather had two or more sons, one of which, of course, was Kuchel and Kenny's father. One of the other sons settled near the wall in Shiganshina. He was either Mikasa's father or grandfather.
As it turns out, Levi's mother was Kenny's sister, who died when Levi was very young. As his only living family member, Kenny felt he owed it to his sister to look after her son, his nephew. Once Levi was able to fend for himself, Kenny felt he had fulfilled his obligation to his sister and left him.
It is very likely that Levi knew what his mother did for earning money when he was little. And thus, understood that his real father´s identity would be hard to know. His mother died and no one dared to enter their room, no more customers and no more money.
The Overall Theory - Kenny began raising Levi most likely during his pre-teen years. The “abuse” Levi suffered was not physical abuse, but emotional neglect from living with a textbook sociopath.
They don't spell it out, but the implication is that the branch of the family Kenny is referring to is Mikasa's family. Since he uses the term "branch" it's likely not his immediate family (parents and siblings). I figure they're probably cousins, perhaps distant ones, since he doesn't bother with names.
However, it was later revealed that no one had pushed Kenny to his death but that he instead accidentally fell to his death after stepping backwards during a conversation with Konstantin Vasiliev who warned him that The Twelve would assassinate him.
Kenny Ackerman is a supporting antagonist in the anime/manga series Attack On Titan, serving as the secondary antagonist of the Royal Government arc and a cameo antagonist in the flashbacks of the Marley arc. He also makes a cameo in Grisha Yeager's memories during the War for Paradis arc.
So according to the man himself, Levi did feel sadness and a sense of loss at the death of Kenny. Learning Kenny's identity, that he was his uncle and not his father, gave Levi relief.
2 They Are Distant Relatives
In the case of Mikasa and Levi, they share the surname Ackerman. While there's no way they are siblings— they have different parents, after all— there's evidence that the two of them are distant cousins, especially when considering the power they share with Kenny.
Awakened power
Levi Ackerman describes it as knowing exactly what needs to be done, and it lets the Ackermans exhibit physical abilities much, much higher than the average human. Eren Yeager learns from Zeke that this is because they were the result of the old Eldian Empire experimenting with the Subjects of Ymir.
Rod Reiss - Though Kenny initially seemed loyal to Rod, acting as a sort of 'right-hand man' for him, he lacked any respect for the true King of the Walls. He saw Rod as a self-serving coward, incomparable to Uri at least, and only obeyed him to fulfill his dream of inheriting the Founding Titan.
In some apocryphal texts such as the Testaments of the Twelve Patriarchs, and the Book of Jubilees, Levi's wife, his children's mother, is named as Milkah, a daughter of Aram.
Levi's father is unknown. In the Attack on Titan series, it is not revealed who Levi's biological father is.
However, after Kenny revealed to him that he was his uncle in his final moments, Levi found out that he was an Ackerman. This meant that him and Mikasa were actually related, which also explained why they were two of the strongest soldiers in Paradis.
Coon and Friends. Kenny is cursed because his parents used to go to a cult for free beer. Kenny has the power of not dying, whenever he dies his mother will birth another one of him and he seems to grow in the body he was when he last died. Kenny is one of the kids that have a super power.
Viewers have seldom seen Kenny's full face in South Park — with only 12 instances in which his parka hood is not obscuring his face. Parker and Stone do not reveal his face often, which contributes to the character's enigmatic appeal and popularity with the fanbase.
Levi is stronger on all fronts. Kenny is more of an assassin than a fighter honestly. If they both used maneuver gear, Levi would win because small body equals more flexibility (shorter torso means less work on the core the keep balance), faster in changing direction because less mass = less inertia.
Ultimately, he turned out to be a weirdly likeable character who ended up helping the scouts. However, for years he was a fearsome mercenary, nicknamed "Kenny the Ripper". His years of killing caught up to him in the end though as his demise came in the same arc as Rod Reiss'.
Kenny is on the inside, sitting in on meetings, privy to the inner workings of the government. Kenny is with Levi 4 years (I can't imagine it's any longer) Once Levi is old enough to murder an adult man take care of himself, Kenny abandons him.
It was Kenny's wish to become a titan, as apart from the huge power they inherited, he wanted to be effected the way Uri and Frieda had when they inherited the founding titan, meaning they became pacifists and preached about peace within the walls and refused to use their power for violence.
Kuchel Ackerman (クシェル・アッカーマン Kusheru Akkāman?) was the mother of Levi Ackerman and younger sister to Kenny Ackerman. She worked as a prostitute in the Underground city.
After this, Uri, with the knife still stuck in his arm, bowed before Kenny and apologized because of the persecution of his family and his frustrated attempt to create a paradise within the Walls. This heavily surprised Kenny, who wondered how a powerful being like him could bow before someone like himself.