I had an older game with a second-gen teen in the main family. I got back to playing them, got him and his girlfriend to where they can accept early graduation, and they went to university together. At the moment, they've both aged up now, and have a term and a half left to go. They'll get married right after graduation, honeymoon in Selvadorada, and the goal is for them to be in an apartment and her pregnant, in time for the expansion.
My game is modded, so it's not as simple as Try for Baby and it's a sure thing. It might take a lot of trying. Or it might happen when you didn't want it to. You know, kind of like real life...