Superman & Lois - now ALL seasons

I'm still going through the pilot, but I'm a little off on one thing...

I thought Jon was the only biological child and the other child was the one they took with the from the planet that was destroyed. Was everything just retconned on us?

Am I asking a question that will be answered by the time I'm done with this?
Seems like they've changed the story in that regard. At least that what it looks like from episode 1.