Join Date: Apr 2009
Location: Bye Delta
Programs: AA EXP, UA Silver, HH Diamond, IHG Plat, Hyatt Plat, Marriott Titanium, Nat'l EE, Avis PC, Hertz PC
Posts: 16,637
The only way for DL to upgrade both or neither passengers is for them to be on the same PNR. If you are on separate PNRs, you'll each clear at your own priority and one may be upgraded without the other.