A 3-year-old boy was found dead in a Brooklyn home Wednesday — and cops were investigating whether he was beaten to death with a belt by his baby-sitter aunt, police sources said.

Cops found Ethan Ali lifeless and covered in bruises at 287 Rockaway Parkway in Brownsville after a 911 call.

The boy’s mom had left him with the aunt, sources said. The aunt’s boyfriend was also there when cops arrived.

“My nephew, my nephew!” another aunt, Jennifer Evans, cried outside the house.

“I want justice. He don’t deserve that. He’s only a child. He was so vibrant.”

One police source said, “There appears to be a history of abuse against the boy.”

The aunt was being questioned at the 67th Precinct Station house Thursday morning.