The 18-year-old Bronx teen stabbed and burned to death on Wednesday had been dating the accused’s 14-year-old sister, it has emerged.

Winston Ortiz was knifed once in the chest and twice in the back before being set alight on the fifth floor of an apartment building in Highbridge, close to his home.

22-year-old Adones Betances, who lives just five blocks away from the victim, was arrested and charged with murder.

According to the New York Post, the victim’s younger brother Wilmer said Winston had been dating Betances’s little sister — but that she had ended it just hours before he was killed.

“I’m pretty sure this all had to do with a breakup that he had been dealing with yesterday,” he said. “This is [his ex-girlfriend’s] older brother we’re talking about.”

The 17-year-old said he didn’t remember exactly why she’d broken up with Winston, but it had “something about him being too overprotective,” adding: “But I don’t know what that means.”

His brother had been “very emotionally distraught” over the break-up, he said.

It is not known how long the two had been dating; however sources told the publication that Betances was furious over the age gap.

Law enforcement sources claim Betances ambushed Ortiz, walking into the building just ten minutes ahead of him.

They said Ortiz managed to identify his killer before succumbing to his injuries.

Betances meanwhile took his girlfriend to dinner after the attack. He claimed he is being framed.