As the youngest surviving son of Augustus Louis, Prince of Anhalt-Köthen, by his second wife, Christine Johanna Emilie, daughter of Count Erdmann II of Promnitz-Pless, Frederick Erdmann's prospects of inheriting or ruling jointly over Köthen were dim at birth. His situation changed in 1765, after the death of his infant cousin Count William of Promnitz, heir apparent of Pless, left his uncle Johann Erdmann, Count of Promnitz-Pless, without any heirs male; the child's uncle then decided to give Frederick Erdmann the county as an anticipated inheritance. The lordships of Jannowitz, Peterswaldau and Kreppelhof, however, Johann Erdmann gave to his great-nephew Christian Frederick of Stolberg-Wernigerode (nephew and, later, brother-in-law of Frederick Erdmann).
After receiving this inheritance, Frederick Erdmann moved to Pless and assumed the title "Prince of Anhalt-Pless" (sometimes "of Anhalt-Köthen-Pless").[2]
