Master login linking to multiple accounts in e-commerce platform

Please excuse if my question seems too basic.

Our e-commerce platform used KeyCloak as the IdP, but we have an option to integrate with external IdP as well.

One of our customers is using Auth0. Their customer account structure is:
Parent Account
Billing Account1 (Child)
Billing Account2 (Child)
Billing Account3 (Child)

In our platform we cannot maintain this hierarchy and have to create individual accounts for each billing account and with unique username for each account.

But our customer needs a single master login to login to each of these accounts.

Using Auth0 is it possible to link these multiple accounts into 1 Master account ? I’ve attached a diagram to check if that flow is possible, else please advice.