Ronald Syme considers Sisenna's tribe "Galeria" as clear evidence that his family origins lay in Spain, and counts twenty different individuals from those provinces who shared his gentilicium.

[3] Sisenna is attested as governor of Roman Britain in a fragmentary inscription at Wroxeter dated 14 April 135.

Birley speculates that no other person was suitable for the job, and Hadrian appointed him to the ordinary consulship as a means to render Sisenna eligible more rapidly.

[7] Based on the unusual name, he was kinsman to, if not father of, the suffect consul of 146 and proconsul of Asia, Publius Mummius Sisenna Rutilianus.

[6] If they were father and son, that Rutilianus became consul only thirteen years after Sisenna suggests that the older man attained the fasces late in life.