If William Large didn't already have a wife, I would be inclined not to create one for him if I didn't know her name. (Am I the only one who dislikes creating more Unknowns?) You can always include the facts about a spouse on the spouse's profile.
However, since he does have a wife, it seems to me that revising the existing profile makes more sense than creating a new one, and then having to find another (unrelated) profile to merge the discarded wife into.