Originally Posted by
drklain
My understanding is they have to be on the same flight with you but it can be anyone (I use this benefit for co-workers all the time). Do not even need to be on same itinerary, you just need to be on the same flight.
When you do the GS upgrade for a traveling companion, they are already on a separate PNR.
Sadly, this can cause an issue if there is any type of MX or equipment change.