Multiple sub-domains

I’m wondering how to do this for a few sub-domains that I’ve set up for my family members.
For example:
https://site1.domain1.com
https://site2.domain1.com

Should I treat each site as it’s own account and each family member that has their site should sign up with shift8 on their own? Or how would that work? Would shift8 just create CDN’s like https:/cdn.site1.domain1.com