Multiple independent attestation from Paul, Matthew, John (special L), and Josephus — the strongest form of historical evidence — confirms Jesus's brothers including James

Licona summarizes: Paul, Matthew, John, special L material (Luke), and Josephus (a non-Christian) all independently mention Jesus's brothers, all identifying James as one of them. This represents the strongest kind of multiple attestation historians can find — particularly when one source is unsympathetic (Josephus).