Originally a palace during the Roman Empire, the Laterano was the home of the Laterani family who served as administrators for many Roman emperors. Eventually Constantine himself took control of the building when in a final act of juvenile dominance over his rival, he married Maxentius's sister, Fausta, who possessed the deed at the time. I wonder if Maxentius got the message?
In the 4th century, the Laterano became the principal Papal residence, but lost favour after two fires in 1307 and 1361.