Yes. As long as one Delphox is foreign to your game's language and the other Delphox is of the same language, then it will increase your chance of getting a shiny Fennekin. Your shiny rate will increase from 1/8192 to 3/4096. Source: http://bulbapedia.bulbagarden.net/wiki/Masuda_method
It's known as the Masuda Method and in Gen 6 its chances are multiplied six fold which is 6 in 4096 which is equivalent to about 1 in 683.
