Responses
The artist didnt really portray it very well but the warehouse was too dark for Felix to see Isaacs face. Isaac was there on a mission so he 100% recognized Felix and knows he is the father.
In the spanish translations, during the flashbacks, Felix says he wishes he could clearly see the omegas face I.e. he could not.
i dont know i want to laugh or get angry.. its very obvious benjamin is felix child..but well he dont remember isaac too..