I was trying to breed a shiny Rowlet using my female non shiny Decidueye and a Ditto on Ultra Sun and all I was getting was non shiny Rowlet.
When breeding Pokemon, the only two things that can change the shiny rate are the Shiny Charm and the Masuda Method. If you breed a shiny, you are just as likely to hatch a shiny as if you breed a non-shiny.
Usually, each Pokemon has a 1/4096 chance to be shiny. If you have a shiny charm, then the chance becomes about 1/1365. If the two parents came from different-language games, then the chance becomes about 1/683. If both are true, then the chance is 1/512. No matter what you do, you can possibly hatch several thousand eggs without getting a single shiny Pokemon. You just have to keep trying and hope you get lucky.