Complex sentence: The Daughters of Danaus or Danaids (also Danaides or Danaïdes;;) were the fifty daughters of Danaus that were to marry the fifty sons of his twin brother Aegyptus, who was a mythical king of Egypt.
Split into simpler sentences: The Daughters of Danaus or Danaids (also Danaides or Danaïdes;;). The Danaids were the fifty daughters of Danaus that were to marry the fifty sons of his twin brother Aegyptus, who was a mythical king of Egypt.