How did Darth Vader come to be in existence?

Answer 1

Darth Vader (Anikan Skywalker) was mysteriously concieved by midichlorians, the microscopic lifeforms that create the force in the Star Wars Universe. His mother Shmi Skywalker became his only parent.

Note: Some theorists believe that Anikan was in-fact created by Darth Sidious (Emporer Palpatine/Senator Palpatine). This is due to the fact that Darth Sidious' mentor, Darth Plageous taught him through the force the ability to create life. Theorists believe that Darth Sidious put the seed of midichlorians in Shmi (she was randomly chosen) to create the "Chosen One," hoping that he could turn this "Chosen One" to the dark side. A fate we all know could never happen.