Dead Tropes

So we are lying in bed, the kid and I, as we do on Sunday morning, not getting up, and the kid is ranting to me about her Sims adventures, as she is wont to do, and she is explaining how she can't get two of the characters married, due to some "glitch" I am not precisely following.

(I do not play Sims.)

Me: Can't they just live in sin?

The Kid:  Live in Sims?  They do live in Sims.  What--

Me:  No.  Live in sin.

The Kid: ---

Me:  Live in sin.  

The Kid:  What does that mean?