Hi @Wayne Bandy
You can invite your colleague Brian to your team in the Founders Hub Portal; see docs for more details. Once Brian receives the invite, he can accept the invitation to be added. Upon accepting the invite, he needs to have a LinkedIn account to actually log into the portal.
To add him to your Azure subscription, you can follow the steps listed on Tutorial: Grant a user access to Azure resources using the Azure portal - Azure RBAC | Microsoft Learn. The important thing to know is ensuring you add the appropriate role for him.