Hitorigami is a Shinto deity which came into being not in pairs but alone. Generally, those gods who have parents are not called this way.
In contrast, a pair of male and female deities are occasionally called 'Narabigami.'
Another examples similar to this are 'Tomoni narimaseru kami' and 'Tagui narimaseru kami' (kami which came into being in pairs).
Kotoamatsukami (Separate Heavenly Kami)
Kamiyonanayo (Seven Generations)