Double-Barreled Surname

[Cassie]

Call me slow, I'm only just really getting into the game since it stopped crashing on me last week. But I have AwesomeMod & IndieMod, so maybe this is a feature from those, but my Sims' friend's last name was Langerak, and this Langerak lady [forget first name] married this guy who's last name was Alvi.
Then when I next made my Sim meet up with her friend, her friend's surname was Alvi-Langerak. Is that a feature in the game, to combine surnames? I didn't know you could have double-barreled surnames. How can I get my own Sims that I'm playing to do that, anyone know?