How did the human lineage continue after Cain killed Abel, knowing that Abel had married his sister, and what was the duration between Prophet Adam and Prophet Noah?

There is nothing in the Qur’an or Sunnah to indicate that Adam’s offspring were limited to Cain and Abel. Rather, Adam and Eve had many children. Historians have mentioned that Eve bore Adam one hundred and twenty sets of twins, or forty males and females in twenty sets of twins.

Some scholars are of the opinion that the lineage of all humanity traces back to Seth, son of Adam, and that the descendants of Adam’s other children, besides Seth, all perished and became extinct.

As for the period between Adam and Noah, peace be upon them both, it is mentioned in a hadith authenticated by some scholars as ten centuries.