- The suspect, along with his two younger siblings, became the most notorious gangster in the district.
- The suspect, along with his two younger siblings, became the most notorious gangsters in the district.
I know that grammatically, it should be gangster and not gangsters because phrases such as “along with”, “together with” and “as well as” introduce a parenthetical phrase and do not modify the subject, but still I find this usage confusing. To me, the three brothers became notorious gangsters not just one.
Could anyone help provide more insight?