If the doorbell is already setup, you can't and don't need to use the setup steps to add it to the app on more phones.
To share the doorbell with your family member, invite their account/email address to the home:
Share a home and devices in the Google Home app - Google Nest Help
The email address you invite must be a personal Gmail account, or if the person you’re inviting to the home uses another email provider, they must create a Google account using that email address. Once they receive and accept the invite, your doorbell (and other devices you may have in the app) will show up in their Google Home app.
