[Albion Wilde]

the only abortion was Michael second son in Godfather II. Sonny's out-of-wedlock son has the conflict with Joey Zaza, and Michael's eldest son is the opera singer.

The abortion reveal came at the end of Godfather I. Sonny's out-of-wedlock son (played by Andy Garcia) and Michael's son's career as an opera singer don't show up until Godfather III.

[Dr. Sivana]

The abortion reveal came at the end of Godfather I.

Which version are you talking about, some TV reordering? The abortion is squarely in the middle of Godfather II. Sonny's out-of-wedlock son was conceived (I have heard) during Connie's wedding reception in Godfather I.