Bastard Homunculus: Reborn in the Corpse Pit - Chapter 6: The Irregulars(Part 1)

“A cheat system? Do you take me for a fool? Nowadays, where can you find such a good thing falling into your lap? Scram from my head. Is this is new kind of fraud? Or is this a murderer training system of aliens that contains the ability of hypnotism?”

“No, I am the chaos that whispers from nothingness, the nightmare of all living beings in the Southern Ten Stars, the successor of the unparalleled God and… your elder sister.”

“…I only have a younger sister, I don’t have an elder sister!”

“No, you have one. I am an illegitimate daughter. It’s just that your dad didn’t inform you.”

- Description from Novelupdates

There was a Senior Brother and a Junior Sister. One of them was transmigrated to this world and had cheats while the other was the reincarnation of a Great Emperor.

Baek Yigang is a son of the Baek Clan, one of the seven great clans of Zhongyuan. Afflicted with the Taiyin Qi Blockage, he is cursed with a shortened lifespan and the inability to collect internal energy. He had been peacefully spending the rest of his days indoors when he was ambushed by a group of masked people. During the ambush, he lost his servant who was like a sister to him. Chased by the attackers, Baek Yigang escaped through a secret underground path. When he came across a blocked path, he decided he’d at least die fighting and picked up a rusted sword that was stuck in the ground…

Adam, who mysteriously transmigrated to the Marvel universe over a decade ago, has established the powerful Umbrella Corporation. Now, he's unleashing a new era of viral evolution. The Progenitor Virus, T-Virus, C-Virus, and G-Virus are just the beginning of his sinister plans.As heroes and villains struggle to contain the chaos, new threats emerge: the Blacklight Virus, Z-Virus, and the dreaded Cthulhu Virus. Adam's shadowy influence grows, pushing the Marvel universe to its limits.