Can I create an email address for a family member on my private domain if they don’t have an iPhone or Apple product?

Hello DjPunchNY,

Accessing the email relies on having iCloud access. Per Set up a custom email domain for iCloud Mail on all your devices - Apple Support:

After you set up a custom email domain, you can send and receive mail from that domain on your iPhone, iPad, iPod touch, Mac, and Windows computer, and on iCloud.com. Make sure you’re signed in with the same Apple ID on each device. If you have devices where you’re not signed in with your Apple ID or that have the Mail feature turned off, you won’t be able to see your mail on those devices.

Thanks for using Apple Support Communities!