The Lagid (named for Ptolemy I’s father) kingdom started with Ptolemy I, who realized the advantage of a kingdom in Egypt – mainly that it was easy to defend.
His son, Ptolemy II, is credited with finishing the Pharos (lighthouse) of Alexandria and the Library at Alexandria. He was also the first Ptolemy to marry his sister.
Ptolemy III nearly defeated the Seleukid empire, but was forced to turn back due to an uprising in his own Egypt.
Berenike II was the wife of Ptolemy III. She killed her first husband when she found out he was cheating on her.
Ptolemy IV was the beginning of the lazy kings of Egypt and started its downfall.