Thomas Aquinas was very clear that no angel or demon could ever produce a child. Procreation is a natural biological power that angels and demons do not possess. The only possibility Aquinas allows is if a demon assumed the form of a woman (succubus) and had intercourse with a man and then transformed itself into the form of a man (incubus) and impregnated the woman with the man’s seed. In this way a child could be conceived, but, Thomas wrote triumphantly, it would not be the child of the demon but the child of the man! There are no demon-children, only troubled children who have been demonized.

David Albert Jones, Angels: A Very Short Introduction (2011)