Can Android user be invited to Family Group and share Apple Card?

No, that’s not possible. They must accept the invitation on an iPhone.

https://www.goldmansachs.com/terms-and-conditions/Apple-Card-Customer-Agreement.pdf

>> What you need

• Own a compatible iPhone or iPad with the latest version of iOS or iPadOS, or a compatible Apple Watch with watchOS 7.5 or later. 
• The account owner must have an Apple Cardaccount.
• Set up Family Sharing or be part of a Family Sharing group.
• Account co-owners must be 18 years or older and a member of your Family Sharing group.
• Participants must be 13 years or older and a member of your Family Sharing group.
• Make sure that your device region is set to the United States. <<

Set up Apple Card Family and add a co-owner and participants - Apple Support