The beraita on 63A brings a series of cases where a man say to a woman" You are betrothed after such ocurrence". One of these is "After your sister dies" . Rabbi Yehuda Hanssi concurs with the ruling in this case only, according to Rashi, "Mishum Eivah".
Questions:
A) Is this another case of Afkinhu Rabbanan? As we know "Mishum Eivah" is a reason for Rabbinical enactments!
B) Another case mentioned there is "After your husband dies". Rabbi Yehuda Hanssi doesn't agree that this condition is invalid. Is this because the relations between a husband and his wife must have a considerable amount of "Eivah" before this Betrothal - otherwise the woman wouldn't agree?
Yeshayahu HaKohen Hollander
A) I don't think one has to invoke the novel aspect of Afkinhu (though the mechanism being used is somewhat similar to Afkinhu), as in all of these cases Kedushin is not immediately Tofes in any event.
B) I don't think that Rashi is explaining the case of "your husband dies" differently than the case of "your sister dies." This explanation is consistent with the Gemara in Bava Metzia (12b) that there is not normally Eivah by a husband and wife, which is the reason why Chazal said that the Metziah of a wife is acquired by her husband in order not to promote Eivah.
All the best,
Yaakov Montrose