He was born. Is it active voice or passive voice? If passive voice then what's it active voice?

Active: somebody does something
Passive: something is done - (by whom may or may not be emphasized)

"Avoid using the passive voice." - active - subject: you (imperative) - verb: avoid
"Use of the passive voice is to be avoided." - passive - subject: use or using (gerund) - verb: some form of to be

To make the active voice, you have to know who bore him. Or you could use another verb: "He came into this world."