Question

Is the chance of getting a Volbeat or Illumise from an egg determined by anything?

Answer 1

There is an even chance for an Egg produced by a Illumise to hatch into either Volbeat or Illumise, regardless of the second parent. Volbeat can also produce Illumise Eggs, but it must breed with Ditto to do so.

Pokemon breeding (Bulbapedia)

Answer 2

Its always the female. So if you want volbeat, breed with ditto.

Comments

This is correct except for the special cases of Nidoran and Volbeat/Illumise.