Species don't necessarily have to be that closely related to hybridize. Compatibility is usually more complex but sometimes surprisingly more crude (when related simply to chromosome number) than a linear scaling with evolutionary time. Goats and Sheep are both in family Bovidae subfamily Caprinae. The species diverged around 7 million years ago [0]. Intra-familial (but inter-generic) hybrids are fairly well-known (savannah cats, zedonks, etc.).

Much more surprising is that people have reportedly successfully created hybrids [1] between chickens (family Phasianidae) and guinea fowl (family Numididae), which diverged around 50 million years ago [2].

Note that http://timetree.org is a beautiful service for finding out how closely related two species are (in evolutionary time).

[0] http://www.timetree.org/index.php?taxon_a=Ovis+aries&taxon_b...

[1] http://biology.stackexchange.com/questions/2592/is-sexual-re...

[2] http://www.timetree.org/index.php?taxon_a=Gallus+gallus&taxo...