Laodice I married her paternal first cousin Antiochus II Theos before 266 BC as his first wife.
Antiochus made peace with the Pharaoh by divorcing Laodice and marrying the daughter of Ptolemy II, Berenice, with the understanding that any children born from their union would inherit the Seleucid throne.
In their divorce settlement, Antiochus gave Laodice various land grants throughout Anatolia which are known through inscriptions.
[15] She may have been given the revenue of two harvests with which to pay a nominal purchase price to set at the valuation of the land for tax purposes.
[11] In July 246 BC, Antiochus II died (some suggest that he was poisoned by a revengeful Laodice) leaving a confusing dynastic situation.
Seleucus II succeeded his father as king and his brother Antiochus Hierax was named co-ruler in Sardis.
[2] Laodice, either for revenge or to prevent civil war, had Berenice and her son murdered in the late summer of 246 BC.
[11] Out of his outrage, the brother of Berenice, Ptolemy III, declared war the same year and invaded the Seleucid Empire.
This occurred in 244 BC which caused a civil war for the next 17 years between Seleucus II and Antiochus Hierax.