“I never heard about a pidyon being required for a second child if the first was by C-section.
Correct. Although it is a machlokes in the Gemora if the firstborn son was delivered via Caesarean section if the second child (assuming its a son and is born naturally) requires a pidyon. We pasken not.”
Thank you, Joseph. I guess I learned it incorrectly. It only serves to underscore how RARE a pidyon haben is.