Even if you have a Priority Club account and Gold or Platinum status, it might make sense to sign up a family member as well for all the bonuses you can get. This works especially well at the properties where there are not any benefits for being a Gold or Platinum member.
I just had a stay with a family member at a Holiday Inn Express location. I signed up for all the one time bonuses that you can find here and for other ongoing bonuses that you can find here. Also, the property in question was offering an opening bonus of 2K Priority Club points per stay.
All the bonuses except the Anniversary Bonus Offer & Elite Member Next Stay Bonus-posted. The 2K opening bonus from the property should post separately in couple of weeks.
It can make sense to open a Priority Club account for a family member as well to take advantage of the available bonus offers.