Unless the Incubus slept with a succubus then the succubi would give birth to a new incubi or succubi.
These human/incubi or succubi hybrid is called a Cambion. The child is taken to Hell to be trained and raised as a member of their race. When they do, they will obtain supernatural abilities and can become extremely persuasive. These births always result in either a pureblood Succubus or Incubus being born, and always kill the mother. Incubi, unlike Succubi, are able to reproduce with females. When a human has intercourse with a succubi/incubi over long amounts of time (say a month) they will start feeling a need for more sex with the incubi/succubi or go insane from how much life force they have lost. They appear to know a myriad of information on topics of politics, theology of various religious, and demonology of the Judeo-Christian faiths. Incubi are often incredibly handsome, slim, and athletic men, cultured and highly intelligent. Moreover, the Asmodai consisted of both incubi and succubi, the latter of which were a lesser species of the Lilim, the first and strongest of the succubi that came into existence when Lilith mated with Samael. It is said that the incubi were also known as Asmodai which are considered a second horde of demons that were birthed from Lilith after mating with Asmodeus.
The origins of the incubus are unknown, though it is more than likely that they originated from Lilith or one of her sisters. However, whereas Succubi target men (and often have an easier job), Incubi target women. They possess many of the abilities of the succubus, including their ability to take vessels and their supernatural ability to seduce.