I send a email to park canada, the following is their reply:
In response to your e-mail, we did recently implement a change to our
family/group definition. A family/group pass still permits entry up to
7 people within a single vehicle, however, the number of adults or
seniors within this group is now restricted to 2. The only exception to this
would be the entry gates to Banff and Jasper national parks. To avoid delays
and backing traffic up into the Trans Canada and Yellowhead highways, the
requirement to confirm the limitation of two adults or seniors would be
waived at busy times of the year.
You did not indicate which national park(s) you will be visiting, however,
if it is the Mountain Parks, it is possible that you and the other couples
you are travelling with may gain entry under a single family/group pass.
At all other national parks, you will be required to buy separate family/group
passes for each couple.