So these two people get married and have a Star Wars wedding. The groom dresses up as Luke Skywalker and the bride as Princess Leia. The wedding program included a FAQ, including one on why would they have dressed as brother and sister.

The answer was that the Han Solo costume would look silly in a wedding and that they were just dressing as characters from the Star Wars universe, not pretending to be characters in it.

Oh. Thanks for clearing that up!