Thanks for your quick reply.
Yes, they indeed can do this, but my wish is that they don’t “have to” do this: automatically, if you create a profile on one site (site A), the same profile (with same password) is created on the other site (site B).
At the end, a profile created either on site A or site B will work on both sites A & B without having the user recreate his/her profile.
Sites A & B have different domain names.
Thanks again for any help you can provide!