Is it permissible for me to marry two sisters?
If I marry a woman and then divorce her, then she marries another man and I marry her younger sister after a while, is this permissible?
It is impermissible for a man to marry two sisters, maternal or paternal stepsisters, and biological or foster sisters, at the same time. This is according to Allah's saying about those who are prohibited to marry,
...and two sisters in wedlock at the same time
However, it is permissible to marry one of the sisters, and if she dies or he divorces her and her `Iddah (woman's prescribed waiting period after divorce or widowhood) comes to an end, it is permissible to marry her younger or elder sister. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.