Flames erupted around 11 a.m. inside one of those buildings; all three are connected through a cockloft. There was a partial collapse of the roof.
The fire, which was under control by 1 p.m., is believed to have started in the middle house, No. 1230, and spread to two other buildings.
Nearly 140 firefighters responded to the scene, and crews remained afterwards to put out hotspots.
In all, nine people suffered minor injuries, including five firefighters. All were taken to Kings County Hospital to be checked out.
The cause of the fire remains under investigation.
All three buildings were heavily damaged in the fire.