Complex sentence: Theodore II Doukas Laskaris was the only son of Emperor John III Doukas Vatatzes and Eirene Laskarina, the daughter of Emperor Theodore I Laskaris and Anna Angelina, a daughter of Emperor Alexios III Angelos and Euphrosyne Doukaina Kamaterina.
Split into simpler sentences: Theodore II Doukas Laskaris was the only son of Emperor John III Doukas Vatatzes and Eirene Laskarina, the daughter of Emperor Theodore I Laskaris and Anna Angelina. Anna was a daughter of Emperor Alexios III Angelos and Euphrosyne Doukaina Kamaterina.