So if you ever heard of Masaya Hokazono? He made a lot of Manga like girlfriend,Inugami and it;s prequel Ingami Kai,and many others. He also made Horror manga one of which is Freak Island and It's prequel Offal Island. Masaya watched a lot of horror movies so the story being Freak Island and it's prequel is that it is about a family of cannibal mutants who also uses a cult and worships a deity called zanta Maria. It is basically Texas Chainsaw massarce,Wrongturn,The Hills have Eyes,Resident evil,and Silent hill mixed with supernatural J-horror.
The members include Yoshikazu the father,Mariko Glaccias the mother,Otoki the grandmother,Mari the eldest daughter,Kaoru the oldest son,Anna and Kanna the twin sisters,and Satoru the youngest.
Anyway the freak Island manga series is still ongoing with 114 chapters and having the 13th volume coming on september 15th, while the prequel Offal Island was completed with 4 volumes and 30 chapters. Anyway I can't get into spoilers but it is really funny and i recommend those who like horror mangas.