Some of the commercial hatcheries also produce what is sometimes called a Commercial Black or Special Black hybrids, as well as the red and white hybrids.
If these were said to be good layers, it is possible, quite possible, the eggs came from a commercial source. Time tells all things.
Sure, I bet you'd like to keep them.
I have both breeds in my coop. The black one is a Black Australorp and the red one is a Red Star. Great birds and co-habitate well together. My Red Star's are the more adventurous off the two breeds. They seemed to be the first to do everything. The Australorps tend to be more friendly and more receptive to petting.