GRUESOME FAMILY BLOODBATH!

PECULIAR ex-preppy Matthew Hertgen slaughtered his little brother, likely ate his slain sibling’s missing eyeball — and fatally torched the family cat at their wealthy parents’ Princeton pad, law enforcement sources say.

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Monstrous Matthew, 31, used a blade and a golf club to slash and batter 26-year-old Joseph Hertgen, New Jersey cops charge — after reportedly posting bizarre poetry on social media that included violent verses about “knives sharpening” and “blood oozing out” of eyes.

Lawmen say the bearded brute called 911 to report a body and a fire at the chichi Michelle Mews apartment complex — and responding officers found a bloody knife, fork and plate near Joseph’s corpse, as well as the charred kitty.