He was also appointed marshal of "Romanie" - a term very vaguely used, but apparently signifying the mainland of the Balkan Peninsula, while his nephew and namesake, afterwards prince of Achaia, took a great part in the Latin conquest of Peloponnesus.
Other brothers were Demetrius, prince of the Morea until 1460, and Thomas, prince of Achaia, who died at Rome in 1465.
In 1263 and 1264 respectively, Michael, with the help of Urban IV., concluded peace with Villehardouin, prince of Achaia, and Michael, despot of Epirus, who had previously been incited by the pope to attack him, but had been decisively beaten at Pelagonia in Thessaly (1259); Villehardouin was obliged to cede Mistra, Monemvasia and Maina in the Morea.
His original map, which was probably intended to illustrate, above all, the distribution of the Apostolic missions throughout the world - depicting the head of Peter at Rome, of Andrew in Achaia, of Thomas in India, of James in Spain, and so forth - has survived in ten more or less modified copies.
On the one hand, five new provinces were added to the Roman dominions - Macedonia and Achaia in 146, Africa in the same year, Asia in 134, Gallia Narbonensis in 118, Cilicia probably in 102.