DJ Khaled’s fiancee’s brother was murdered after an alleged drug deal gone bad.

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. 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.