I haven't figured out how to breed them, can anyone help me?

They need to be adults, adolescents can't breed. The sylesti you're trying to breed can't be brother/sister or daughter/son. They can be cousins or breed to their grandparents (if memory serves correctly). Hope this helps. ^^

@Insanesanity is there a specific button to make them breed? I want to breed my starter with my tamed.

Hello Thunder,

You have to breed them in the Breeding Grounds. It's under the Explore button on the top bar.
Once in there, there is a drop down box you can choose to select the type, aka...choose Nixi if they are Nixis. Hit update, and you will have two drop down options, where you can pick the male and female you want to breed. If you have them named, it's super easy to find! If not, you'll need to pick their id number.

Hope this helps, feel free to pm me if you still have issues :)

What they said. Explore > Breeding Grounds. Then select the species and the male and female pets you want to breed. They can't be father/child, mother/child, or siblings but I think anything else can breed with each other. ^^