Did they hatch from white eggs?
If they are indeed Buttercups, which I very much doubt they are, the breed is called Sicilian Buttercups, not Italian Buttercups. The chick down is not consistent with Buttercups (I breed and raise them).
This is what they should look like as chicks.
Yours lack the correct markings around the face and the down pattern isn't quite right.
As they continue to feather out, they should look like this.
You can see the pattern on the head is still there until it is replaced by feathers. While the birds in question have willow legs, which is correct, that is not a true double comb. It appears to be modified, which means they carry another gene for comb type. Feather coloration is also inconsistent with a Buttercup cockerel, and that older bird is most certainly male.
@azygous - You're one of the only other people I know with them. Would you agree?