The connection of Atum and Re, as Atum-Re, makes Shu a 'son of Re' and as such the brother of the Egyptian king (who calls himself a 'son' as well. Shu is depicted in human form wearing an ostrich feather (the hieroglyph for his name), with his arms raised to support Nut above the supine form of her brother Geb.
The embodiment of the sky. In the Ennead of Heliopolis he is the son of Atum and brother-husband of Tefnut. He was one of the first deities to be created by Atum, either from his semen or the muscus of his notrils. With Tefnut he became the father of Nut (the sky) and Seb (the earth). He raised the body of his daughter high above the earth and separated thus heaven and earth.
The name of Shu in hieroglyphs.