Police arrested a 48-year-old man who allegedly stabbed his brother — critically wounding him — during a fight at a Harlem housing project, police sources said.

Marc Brockington plunged a knife into brother Terrance Brockington’s gut as they were scrapping inside an apartment at the Abraham Lincoln Houses on Madison around 2:30 a.m. Wednesday, sources said.

Paramedics rushed Terrance, 50, to Harlem Hospital where he was listed in critical condition.

Police recovered a knife at the scene and took Marc Brockington into custody. Charges against him are pending, sources said.