senior (at work or school)

junior (at work, school, etc.)

I ②we

someone who is greatly one's senior

producing (people) in great numbers

young person

inexperienced person

person older than oneself (who has more life experience)

fellows

air of seniority

I Am a Cat (1906 novel by Natsume Soseki)

persons of the same age

small fry

colleagues

person much older than oneself (who has much more life experience)

underling

worldlings

comrade

underling

inferior

comrade

party (of people)

lawless people

suffixed to words indicating a class of people to create a plural (esp. in impolite contexts)