Originally Posted by
xliioper
To preferred seats, yes, but not to C+ (which are also preferred seats, but different rules).
For C+, with more than 1 companion, everyone on the PNR needs to be a medallion member, and everyone on the PNR defaults to the lowest tier medallion status in the PNR for upgrade priority. If one on the PNR is general member, everyone is out of luck unless you split off reservations.