Board Thread:General Discussion/@comment-68.228.239.233-20130213065350/@comment-14639380-20131002215034

Redglitch, Parents being in the same family will increase the shiny and shadow chance of the egg by 1%. A parent being shiny/shadow will increase the chance the egg will be shiny/shadow respectively by 2% per parent that is shiny/shadow. Holding a Gold Incense/Dark Incense will also increase the chance of the egg being shiny/shadow respectively by 4% per item.

An example of the highest percentage you can get is both pokemon being from the same family, both being shiny, and both holding gold incense. This would give you a 13% chance for the egg to be shiny and a 1% chance for the egg to be shadow.

Your chance of breeding a shinyis 12%.