The city won’t oppose a druggie gun peddler’s petition to prove that he’s the biological father of tragic 6-year-old Zymere Perkins.

Nicholas John, who pleaded guilty to slinging illegal weapons on Nov. 7, suddenly surfaced just weeks ahead of a deadline to sue the city over the child’s death.

Zymere’s battered body was found in his mother’s Harlem apartment in September. The mother, Geraldine Perkins, and her boyfriend have been charged with endangering the welfare of a child.

John’s suit indicates that he intends to cash in on the tragedy, by suing the city’s child welfare office, the NYPD and a social services nonprofit for failing “to prevent the child abuse that led to the wrongful death” of the boy.

John, a 30-year-old Queens resident with a 10-year rap sheet that includes charges for selling narcotics, admits that his name isn’t on the boy’s birth certificate.

He needs a DNA test to establish paternity, but city Department of Correction officials refused to give him one without a court order, according to his lawyer Abe George.

On Friday, DOC lawyer Lynelle Maginley Liddie said in an email filed in court that the “Department does not oppose your motion” for the order.

“There is no basis in law to deny him access to DNA testing to try to prove paternity,” a Law Department spokesman said.

A judge still needs to approve the request.