I used a travel agency which did the cancelling on 1 ticket (when my grandma passed away) and my mom had to stay behind but my dad and I flew back. we were all on the same PNR so it is possible.

In a different scenario with AA, I had all of us (mom and dad) on the same PNR as well. at the airport, I asked how I can salvage the other tickets as my parents couldn't travel so they bumped me out of the PNR, gave me a new one, then put theirs on a missed flight situation. they basically rebook them onto the next available flight while I flew.

Hope that helps.