At the Foro Boario mithraeum, an inscription informs us the sanctuary was constructed by a citizen with the permission of a priest named A. Sergius Eutychus sometime in the latter half of the third century. Whether this priest held a Mithraic grade is not mentioned, although it is not long after this that the dedication of Severianus, which refers to him as pater sacrorum, was made, while some of the later senatorial Mithraic adherents also use this title, thus it would seem likely that this man did serve as a pater and the title listed here was an adaption that became increasingly common in later periods. Another pater of this Mithraic community was also named on an inscription, although only fragments of this survive, while two other altars and a relief from the mithraeum attest to three men who look to have been citizens.
—David Walsh (2016) Development, decline and demise: The cult of Mithras ca. A.D. 270-430
Other brothers from Roma
The Mithraic fellow P. Aelius Urbanus mentions that he built the sacred area of the Mithraeum Circo Massimo.
Soli invict[o Mithrae] / sacrarium [fecit] / P. Aelius Ur[banus or Urbicus] / sub A. Sergio Eutycho / sacerdote.
To the invincible sun Mithras. P. Aelius Urbanus built the sacred area when A. Sergius Eutychus was priest.