Who were Achilles' parents? Who were the children of Gaia? Were any of #1 the children of #2?
Achilles
Was Achilles a direct descendent of Gaia?
Achilles was the son of a Nereid.  The Nereids were the 50 daughters of Nereus. Nereus was the eldest son of the union between Gaia and Pontus.
Greek mythological hero