Did Cain really exist?

Since some biblical characters, like Kings David and Solomon did exist, but others didn't ( I am assuming that Noah didn't,for instance, although some people think he really lived a lot of years ago) I was wondering ... Did Cain really exist ?? Is he really buried in Kabul ?? The story goes like this : Cain travelled to the actual Iran, and somehow he found redemption for his great sin. Nowadays he is buried in a cemetery in Kabul beneath a mosque of Muslim religion. https://www.mitele.es/programas-tv/cuarto-milenio/temporada-19/top-videos/tumba-cain-kabul-40_012353011/player/