It wasn't as if Ptolemy went to Egypt alone with his wife and children; he went with his army and after establishing his kingdom invited even more Greeks to live in Egypt as well (who arrived in the tens of thousands). The Greeks of the Ptolemaic Dynasty formed the ruling upper class and ran the government in all but lower level positions. The Ptolemies did adopt Egyptian religious customs and called themselves pharaoh but Hellenistic society existed apart from Egyptian. They also adopted the Egyptian custom of intermarriage so most of the Ptolemaic line was brother marrying sister or uncle marrying niece. They barely married outside the family let alone outside of Greek society. Cleopatra is said to be the first of the Ptolemaic line to even learn the Egyptian language. There were many civil wars and uprisings by the native Egyptians so they never accepted the Greeks as native and the Greeks lived apart from the Egyptians carrying on Greek dress, customs and language and thought of themselves as Greeks.