Three months ago, arriving at YQB, everyone was told to approach separately, so my wife and I did go alone to the agent. In another line was a young Canadian woman in a wheelchair who was being pushed by her friend. The agent rather harshly told the friend to get back in line after the wheelchair bound traveler reached the podium.

This is the only time I can ever remember not approaching with my wife at any POE. On the rare occasion that we travel with our adult children, they usually go alone, but my wife and I stick together.

If you are assisting someone who is physically infirm, I'd say go together, and wait to see if you are told to separate. If you are entering a country that allows multiple family members on an entry form, everyone listed should go together. Unrelated adults traveling together will not be using the same form, and should approach the agent separately. At least that is the way I would do it.