Complex sentence: Her scheduled marriage is mentioned in the text as the third union between Stilicho's family and the Theodosian dynasty, following those of Stilicho to Serena and Maria, their daughter, to Honorius.
Split into simpler sentences: Her scheduled marriage is mentioned in the text as the third union between Stilicho's family and the Theodosian dynasty. Following those of (1) Stilicho to Serena and (2) Maria, their daughter, to Honorius.