Based on a part of 'Three Boys' 1670 by Bartolome Murillo -

 the black boy who has his hand out for food. Beerens has transformed him into a hungry black sheep standing on barren ground.

the white boy who might be picking the pocket of the black boy, and who is looking very mischievous. Beerens has transformed him into a white sheep looking sly, with a fox's tail.

A black sheep on barren and stony ground, a white sheep, placed opposite, on green lush grass, and a third sheep with a fox's tail grinning mischievously. 

The black sheep is asking for food, the white sheep is refusing it. Who knows what the other white sheep is doing.