Theodore Komnenos Doukas
Alexius Slav was married twice: first to an unknown illegitimate daughter of Henry of Flanders and then, after her death, to the daughter of a Petraliphas, brother-in-law to the ruler of Epirus (and after 1225 Emperor of Thessalonica) Theodore Komnenos Doukas (perhaps the "sebastokrator" John Petraliphas). The sources give no information about any progeny.