Silkies and cochins were both bred to be good setters and moms.
My silkie will start to sit on any two eggs that accumulate, and has even gone broody with no eggs to sit on at all.
ETA: And to add to what hinkjc said, I have a few EEs, and the most Ameraucana-type one goes broody a lot, and is really tough to break out of it when she goes.
With the silkie, removing her from the nest persistently through the day will break her of it most of the time. When that one EE goes broody, it takes a cup of ice cubes under her a couple times a day to do it.