Early in their reign, before they established the Tetrarchy, Diocletian and Maximian sought to strengthen their rule through reference to collegial fraternity and the divine. Since both aspects were central to the representation of these emperors, our discussion of the dynastic element, their fraternity, will benefit first from an explanation of their divine associations. Specifically, sometime before 289, Diocletian and Maximian adopted the signa Jovius and Herculius respectively, evoking the supreme god Jupiter and his heroic son Hercules. It was unprecedented for emperors to adopt theophoric signa, and the new names implied a close association with the gods being referenced. Jupiter and Hercules appear on the vast majority of Dyarchic and Tetrarchic coins that honour deities. They are often labelled as conseruatores Augustorum (preservers of the Augusti). Jupiter is the deity to most frequently appear on coins of the eastern mints, and Hercules is the most common in the west. An early aureus type makes clear the parallelism between the Augusti and their divine counterparts. Illustrated on the reverse are the standing figures of Jupiter and Hercules, clasping hands and accompanied by the legend uirtus Augg. Clearly, the image is a divine imagining of Diocletian’s relationship with Maximian. Maximian’s panegyrists in 289 and 291 interpret the signa in terms of a genetic relationship, in which Hercules is the ancestor of Maximian and Jupiter that of Diocletian. For both speakers, the emperors possess the qualities of their namesakes, and the speaker in 291 uses the signa to effectively equate the emperors with the gods and present the rulers as divine and omnipresent. The names were also inheritable. Constantius and Severus adopted Herculius, Galerius and Maximinus adopted Jovius, and the panegyrist Eumenius refers to Hercules and Maximian as Constantius’ grandfather and father respectively (Pan. Lat. 9[4].8.1). The names themselves are rare on coins, absent from papyri and appear on almost no imperial pronouncements or other legal sources, the exception being a letter of Jovius Maximinus Augustus quoted by the contemporary bishop Eusebius (HE 9.9a.1). Roger Rees thus wonders whether the signa ‘were considered too informal or modish for certain media, with a cachet suited only to particular levels of discourse’. This may be correct, but of the ten confirmed Latin attestations in inscriptions, two can be considered official usages of the signa, since they were apparently dedicated by the rulers themselves (with the emperors’ names in the nominative), and one formed part of a triumphal arch (ILS 634, 659).