She is an OEGB x barred rock mutt. Her babies are all mixed back OEGB, We have a couple different color OEGB roosters. Likely some of the eggs are hers, but the others will sneak into her nest and add to her clutch. I've had it happen with other broody hens we've had.
In fact, one small black OEGB hen has 4 standard sized roosters she walks around with. They look like they are body guards or something, but they are her sons.