I want to add a Co-owner Apple Card

Yes, but they have to qualify financially as a co-owner because each co-owner must be financially responsible for the entire balance on the account. If something happens to a co-owner, the other co-owner must pay for the entire balance, not just their charges.

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

A credit score is not the only factor used to determine the financial eligibility of an applicant to be a co-owner. Goldman Sachs will look at many factors including income, occupation, credit history and many other factors. A co-owned account can damage a co-owners credit as well. Accounts that aren’t managed could potentially lower both co-owners credit score.