Constantius Gallus, Bruder oder Halbbruder Julians?

According to Timothy D. Barnes, Gallus and Julian are not half-brothers but both are children of Basilina. The only source backing this claim is a fragment of Philostorgius (Hist. eccl. II, 16a, 3) from the Passio Artemii that, however, does not prove anything against the more important testimonies of Ammianus (XIV, 11, 27; XXV, 3, 23) and Julian’s Misopogon (22, 352B). The precise relationship of the two anonymous siblings of Julian is unknown except that they have the same father but not the same mother as him. The study also offers minor corrections and additions to the RE and the PLRE.