This is from Nerd Wallett. You do have to call and link your accounts, and you can only do it once.

You can also combine points with a family member. For example, one spouse with a Chase Sapphire Preferred® Card card and one with a Chase Sapphire Reserve® might each earn points through their own spending. When they want to take a trip together, moving all the points into the account means all the points are worth 1.5 cents each when booked for travel through Chase.