Eligidio Lind of Manhattan was arrested and charged with two counts of second-degree murder, manslaughter, arson and criminal possession of a weapon.
Officials discovered the body of Luisa Rodriguez, 32, inside an apartment at 3034 Albany Crescent Thursday while responding to a fire.
Rodriguez was found with stab wounds near a smoldering mattress along with her 1-month-old daughter Angela, who later died at the hospital.
"It appears a woman was murdered with some sharp object, and it appears she was dragged to the bathroom and the bathroom was lit on fire," said FDNY Deputy Chief Joe Saccente. "The woman was underneath a burning mattress in the bathroom."
Fire officials said Rodriguez died from blunt force trauma in addition to the stab wounds.