Yes, and if they have 2 different google accounts, open one google calendar's settings on a PC and share the calendar to the google account on the other phone - that way just the calendar is shared. If you want the calendars to sync to both phones you need to do this in both directions. You cxan also control, in the settings, whether the calendar from one account can be edited (or not) by the second account.
Bit of a pain to set up but it works well.
Roger