Octopus card can be used twice at one time?

If you just use the card for airport shuttle bus, you two can use one, because you just need to tap once when you get on the bus.
But I should remind you that you need to wait for some time between two tap.
The card cannot be used by two people if you want to take the local metro or buses charged by distances or station.
In my opinion, you had better got two cards seperately, otherwise, it will be very inconvient.