Can A Mule and Another Mule Breed? Or A Mule And A Horse Or Donkey?

A mule is the hybrid offspring of a male donkey and a female horse. Like most hybrids, they are usually sterile. However, on rare occasions a female will be fertile, and can be bred back to a male horse or donkey. There is no record of fertile males, so you could never breed a male mule to a female mule and produce a baby mule - you can only produce a mule by mating a male donkey to a female horse. Note that the reverse pairing, a male horse and female donkey, produces a hybrid called a hinny.