I'm assuming you are creating a new profile for this person? If so, I would only use one of the possible names as the "Last Name at Birth" and list the other variation in the "Other Last Name(s)" field.
Changing the "Last Name at Birth" is considered a less routine edit than most other profile edits, so changing that field should happen as infrequently as possible.
With that in mind, I don't think it's a good idea to put both variations in the "Last Name at Birth" field using brackets or other method. It will need to be fixed later on, or worse, it never gets corrected.
On the other hand, picking one of the variations has the chance that it could be right and the might not need to change again in the future.