Actually, it's very simple. A Club member can upgrade standby providing that all the Golds and Plat are clear and there are seats available. Gold and Plat can upgrade someone travelling with them on the same flight providing that they have stickers too. The companion doesn't have to be CPlus member.

Which brings me to another question:
I am travelling soon with my family (3). i am the only Gold, so is it possible to upgrade myself and one of them 72 hours prior and the other standby at the airport? (The other 2 are Club). I think I can do that because the upgrade folder said that one can upgrade a companion travelling with them.

Regards,
Empress