Demons produce offspring with many creatures. Demons mate and have offspring with humans the most. 

The rarest hybrid is a demon-werewolf. Demon-witch hybrids are uncommon. On the record, demon-angel hybrids don't exist. Angel hybrids by far don’t exist. The closest known to Nephilim are white witches (as per demon knowledge). Demons find the angels' lack of crossbreeds strange and unorthodox (the demons see the angels as unorthodox and vice versa). 

Werewolf-human, witch-human, and demon-human hybrids are the most common hybrids to exist. Although werewolf hybrids are less common despite werewolf-human being common. 

Hellhounds fall into the category of demons. A hellhound hybrid is unheard of and very rare. Only certain situations can create it. Some young werewolves (newborn bitten or scratched) will try to bond/mate with a hellhound if not knowing of the stark difference. Fae also fall within the category of a demon. 

Fae hybrids are fae-human most of the time. They exchanged fae children for human children. These children are used for food or are given to the king. The king will transform the child into an immortal mixed with the king's blood and the selected demonic mother.