There is no form of entity known as "DBA". DBA stands for "doing business as" and it is used when an individual or business entity uses a fictitious/assumed business name.
A partnership can use a dba name (the same holds true for corporations and LLCs).
The question is whether the 4 individuals have formed a partnership or joint venture. You should ask them if they have and if so, obtain a copy of their partnership/joint venture agreement to find out who has management control. If they are using a dba name then follow your bank's policy on obtaining a copy of the fictitious/assumed business name statement.
If the 4 individuals have not formed a partnership or joint venture, then the odds are they would constitute an unincorporated association. You should check your state's law to find out if the fictitious/assumed business statement statute applies to unincorporated associations as well.