Let's start by defining terms. "DBA" means "doing business as." It does not mean "sole proprietorship" because partnerships and LLCs and corporations can "do business as," or use a fictitious name. The example I always like to use is "Doctors Associates, Inc., d/b/a SUBWAY."
So, don't let "d/b/a" be the determinant of how you set up the account.
If your question is about what you think is a sole proprietorship, it can only have one owner.1 There may be other individuals on such an account as authorized signers, but not as account owners.
If you're looking at two individuals who together own and operate a business, it's a partnership, LLC or corporation, depending on the business form they have chosen, unless state law permits them to jointly operate as a sole proprietor.1
1Some states (Oklahoma is one) have a limited exception to this rule. They permit spouses to own and operate a sole proprietorship if they don't form a partnership. This is a matter of state law. (As spouses operating a sole proprietorship, they would be in a "qualified joint venture" under IRS rules, and would not be treated as a partnership for IRS purposes.) Such an account would operationally and legally be a joint account (owned by two individuals, with rights of survivorship under most state laws) but considered a sole proprietorship (able to hold a NOW account and not subject to Beneficial Ownership requirements).
First published on BankersOnline.com 4/25/11; updated 7/20/20.