They're not siblings.
But they are bros.
General place for discussion about the Chainsaw Man Manga and Anime.
Please be civil and mark spoilers.
They're not siblings.
But they are bros.
Even Makima calls Power Denjis "troublesome little sister"
https://mangadex.org/chapter/eb16a43a-21f5-4c97-b890-7e209f953528/10
I think their relationship is complicated, and that's okay. But ultimately, they're bros.