Gen 2 Doesn't guarantee shiny eggs ever. Breeding a Shiny Pokémon with a Non-Shiny in Gen 2 has a 1/64 chance of producing a shiny. In theory, you could breed 2 shinies to get a higher chance; however, due to the gen 2 breeding mechanics, the game will recognize both Pokémon being from the same family and prevent them from breeding. :P