First, here’s an article with the ins and outs of the new tweaks to the Apple Card to allow multiple users:
And here’s the reason you don’t need to be in a rush to understand the details:
PSA: Apple Card Owners Won’t Be Able to Combine Existing Accounts Until July
Monday May 24, 2021 10:51 am PDT by Sami Fathi
Following its announcement last month, Apple today officially flipped the switch to allow parents to share their Apple Card with their teenagers or friends and the ability for spouses to co-own a single Apple Card account. However, one notable feature that didn’t get released today is the ability for two separate Apple Card accounts to be merged into one.
Apple announced the feature last month but didn’t specifically pin a release date. Now, in a new support document, Apple says that starting later on in July, users will be able to merge two existing Apple Card accounts into one, and in doing so, be able to combine their credit limits.
Coming July 2021: You will be able to invite another Apple Card owner to combine credit limits and form one co-owned account.1