shadow of mars

Hi I have two (2) natu breeding at the daycare, both with the synchronize ability I've bred 20+ eggs (keeping track with the achievement, those are the only ones I have ever bred) and only ONE out of TWENTY eggs came with Sync. All others are early bird or magic bounce. Am I that unlucky or somethings wrong? I've tried breeding with one syncho + one early bird parent but all eggs were early bird as well. This is getting ultra frustating Anyone knows whats up?