Christopher Compton was formally charged Thursday with three counts of murder and 10 counts of arson in Monday's fire on West Franklin Street.
He also faces a charge of being an habitual offender.
A witness says Compton admitted setting the fire while firefighters were still battling the blaze.
The witness also says Compton told him he knew his two young daughters were inside.
28-year-old Keri Jones, her 3-year-old daughter Jazmine, and 76-year-old Donald Lankford died in that fire.
Four other people and six firefighters were hurt.
Prosecutors say they plan to seek life without parole.