When the animals imagine a "family", each one is played by one of the owners, even though they don't know it's really them. Their former owners were likely the most prominent humans in their lives, so it makes sense they would think of humans looking like their owner.
Furthermore, an argument could be made that the scene is imagined by Leroy, who, with his job hauling stolen goods, most likely was exposed to Mordechai's gang regularly. He's imagining this family as the four humans he's around the most (seeing their silhouettes in the same shape as them helps).
