Tiro, Caele'strius
an intimate friend of the younger Pliny. They had served together as military tribunes, as quaestors and as praetors, and were in the habit of frequently residing in each other's houses. (
Plin. Ep. 7.16.) Four of Pliny's letters are addressed to him (
Ep. 1.12, 6.1, 22, 9.5).