If you've already generated the timeline, but need to change the role of the bride, groom, or wedding party contacts, you can navigate to the "edit" tab and scroll down to the wedding party contacts. There, you will see the contacts and their roles. You can click the three dots to the right, select "edit contact" and then change the role from Bride to Groom.

Then, you can navigate to the "Timeline Actions" drop-down menu at the top of the timeline. Select "find-replace." You can easily change the name of the Bride to the name of the Groom throughout the timeline, and vice versa.