Quote Originally Posted by Folgore
Exactly. This become very apparent when taking a closer look at the relations between the Diadochi. Seleucos Nikator for example, his second wife (Stratonike) was the daughter of Demetrios (son of Antigonos Monophthalmos). He was 56 at the time of the marriage, she only 17. (This marriage was only one or two years after the battle of Ipsus, in which Seleucos defeated Antigonos (and Demetrios) and in which Antigonos was killed.) After Seleucos' death his son (Antiochos Soter) married Stratonike (his stepmother).
Actually, the story is much better. Seleukos and Stratonike had a daughter (Phila); and the marriage between Antiochos and Stratonike occured while Seleukos was still very much alive. Seleukos then sent Antiochos off to govern the eastern provinces. The Seleukos-Stratonike-Antiochos marriage triangle was a well-loved source of material for hellenistic authors and playwrights.