Gaile, just a passing thought, not an authoritative opinion on the subject. If you were to associate the two Lukes as siblings, the system would then automatically create its own "Unnamed Father Lukes" profile, and you would not need to do anything further with it until you have more info. There are already lots of those unnamed fathers in the data base, so presumably there is no policy to discourage it.
In this case there's another wrinkle worth noting. If there were children of both of these marriages, the children would be classified as double first cousins, which might be a point of interest to their descendants that would be worth documenting.