Is it OK to marry your wife's sister?
Consequently, when a man's wife dies, if he wish to marry again, he is at liberty to marry any of his wife's sisters by nation or by common sisterhood, but not his wife's own sister by blood (or affinity), because God's law forbids him so to do, she being considered by God near of kin to him through his marriage with ... What do you call someone who is married to your wife's sister?