While they have different editorial staff, the Sun Herald is Fairfax's Sunday paper and the SMH is published the remainder of the week at the same printing facility. You can get combined subscriptions.

And one is a broadsheet and the other a tabloid. Same publisher but quite different beasts.

The publishers of the Sydney Morning Herald used to publish two newspapers daily: the Herald was (and is) their morning broadsheet, and the Sun was their afternoon tabloid. Their Sunday paper was called "The Sunday Sun and Guardian" (probably this came from an earlier paper which had otherwise disappeared), but, back in the late fifties, they dropped the "Guardian" and decided to cash in on the affiliation with the Herald: one Sunday paper (a tabloid) grabbing the readers of both the morning and afternoon papers... the Sun-Herald.

Eventually, the Sun closed down -- with absolutely no notice at all, one afternoon it was on the stands, and the next day it had gone forever -- and now only the Herald remains.... and, of course, the Sun-Herald, which (alas) has a lot more in common with the defunct Sun than it has with its weekday namesake.

And the SMH, originally the Sydney Herald, has the distinction of having been in business since the early 19th century.