How did mankind multiply with only Cain and Abel, and how did the jinn multiply?

Allah honored Adam with Eve, and through her, He blessed him with many sons and daughters. It has been narrated that Eve bore Adam forty children in twenty pregnancies, with each pregnancy resulting in a male and a female. Adam would command each son to marry his sister who was not born with him. And the procreation of humankind occurs through marriage. As for the procreation of jinn, there is no definitive knowledge about its manner, except that Iblis has offspring, as stated in the Quran: "Will you then take him and his offspring as allies instead of Me while they are enemies to you?"