"King Sleep was father of a thousand sons -
indeed a tribe - and of them all, the one
he chose was Morpheus, who had such skill
in miming any human form at will.
No other Dream can match his artistry
in counterfeiting men: their voice, their gait,
their face - their moods; and, too, he imitates
their dress precisely and the words they use
most frequently. But he mimes only men..."
Ovid therefore suggests that Morpheus only sends images of humans in dreams or visions, while his brothers Phobetor and Phantasos are in charge of depicting dream images of animals and inanimate objects. Together these three sons of Sleep - Morpheus, Phobetor, and Phantasos - rule the realm of dreams.
Who's Who in Classical Mythology