Last name didn't change after getting married.
I moved two sims in together and when they got married, the female still has the same last name she did before they got married, and their child has her last name.
Forum Discussion
I'm ole fashioned. I think it should pop up a window when they get married and you can put in what you want it to be. Or ask do you want her name to be _______ or ________ as a choice.
