Relatives which can't be married

And marry not women whom your fathers married, except what has already passed; indeed it was shameful and most hateful, and an evil way.

Forbidden to you (for marriage) are: your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters, your foster mother who gave you suck, your foster milk suckling sisters, your wives' mothers, your step daughters under your guardianship, born of your wives to whom you have gone in - but there is no sin on you if you have not gone in them (to marry their daughters), - the wives of your sons who (spring) from your own loins, and two sisters in wedlock at the same time, except for what has already passed; verily, Allâh is Oft¬Forgiving, Most Merciful.

An-Nisa 22-23