Co parent and lover, what is different if not become both? Is it possible to choose both?
Viewing post in Carnal Voyages - Public Release Version comments
Co-Parent: Slightly changes some dialogue options to indicate you've had kids together, for players who want to roleplay as a parent in a relationship.
Lover: The current relationship state which can change over the course of the game (some work has been done for this but it's not fully implemented yet). You can have a kid with someone you're in a Hate Fuck relationship with, if you want to roleplay a bitter divorcee.