Yes, there have been threads on this before. However, I have a different situation.
These two sims were once married. The husband died, but was resurrected a few days later. He and his wife are now listed as engaged. There isn't an option for them to marry. I also can throw regular parties, but not wedding parties or bachelor/bachelorette parties. They live together, and their household isn't even close to full, so that's not the issue.
The whole thing isn't a game breaker, but they both rolled wishes to get married, and I just really want them to have a great wedding. I don't want to break them up either, but if that's the only way to fix this bug, I guess I'll have to.