DJ Khaled's Fiancee's Brother Murdered In Alleged Drug Deal

DJ Khaled's fiancee's brother was murdered after an alleged drug deal gone bad ... TMZ has learned.

Cops say Nicole Tuck's younger brother, Jonathan, was shot in the face after he allegedly showed up at a Bronx apartment Sunday to buy weed. We're told the apartment was less than a mile from Tuck's home ... he allegedly got into an argument there and was shot. He was taken to a hospital where he died.

Law enforcement sources tell us a 34-year-old man was taken in for questioning about the incident.

Khaled and Nicole had a son, Asahd, in 2016.