Equus Caballus Parkinson Are There Any Species In The Same Genus That Cannot Breed And Produce Fertile Offspring?

Are there any species in the same genus that cannot breed and produce fertile offspring? - equus caballus parkinson

Domestic dog: Canis familiaris. Wolf: Canis lupus.
Horse Equus caballus. Zebra: Equus zebra
Falcon: Falco spp.

These are just some examples of animals in the same species can breed and produce fertile offspring - a feature that until now part of the definition of a species.

Well, I'm not sure that can produce the horses and zebras * * .... fertile offspring
In addition, dogs have apparently been reclassified as a subspecies of Canis lupus.

But whatever the hawks. All species can produce fertile offspring faclon all other types. Can not play so there are all species within a genus, and / or do not produce fertile offspring?