Does «en» always have to replace «de»?

Question

I saw this sentence online «Mon père est médecin et je vais en être un aussi.»I'm confused because there is no «de» to replace?

Accepted Answer

Hi Rike, 
The Kwiziq lesson you are looking for is the following one -
En with quantities = Of them (adverbial pronoun)
Hope this helps!

Answer

Hi Rike,I'm thinking  "je vais en être un aussi"  --> I'm going to be one (en) OF THEM also.Hope this helps?Jim

Answer

Jim is correct: sometimes the "de" which is replaced by "en" isn't literally in the sentence but implied.Tu aimes le café? - Oui, j'en bois trop.Do you like coffee? - Yes, I drink too much of it.