Marriage won't let you change name.

@crinrictAfter getting remarried, there was an unexpected popup (Happened while I was trying to get another Sim to either eat or garden, can't remember) and the game asked if I wanted to change the surname of one of my Sims. I chose to change her surname to the same as the other Sim's. Second time I changed the surname in this way was a first marriage and I changed the name after asked. That was more recent, I think last year. I also decided against doing it with the first Sim's parents, even though the option had appeared.