NEW YORK — A Brooklyn-born soldier slain this week in Iraq was a new father and a model serviceman, mourning relatives said.

Army Spc. Michael D. Rivera, 22, was one of three soldiers killed March 7 when an explosive detonated near their vehicle in Baghdad.

Rivera’s family said the soldier recently celebrated the birth of his daughter.

The girl, named Joycelin, was born Sept. 6 in Korea, where Rivera was stationed. She shares a birthday with Rivera’s mother.

“He was thrilled she was born on that day,” his father, Jose Diaz, told the New York Post. “Because he loved his mother so much.”

After the birth, Rivera was transferred to Fort Hood in Texas, and was soon deployed to Iraq.

His cousin, Edward Rivera, who also served in Iraq, called his relative a model soldier who loved his job.

“I told him, ‘I know from experience, it won’t be so bad.’ I made him promise me he was coming home,” he said.

Rivera was killed along with Army Spc. Shawn P. Rankinen, 28, of Independence, Mo., and Army Staff Sgt. Christopher R. Webb, 28, of Winchester, Calif. All three were assigned to the 2nd Battalion, 5th Cavalry Regiment, 1st Brigade, 1st Cavalry Division.