RELATIVES WHO MAY NOT TESTIFY (Yerushalmi Halachah 6 Daf 16b)
משנה ואילו הן הקרובים אחיו ואחי אביו ואחי אמו ובעל אחותו ובעל אחות אביו ובעל אחות אמו וחמיו ואגיסו
(Mishnah): The following relatives [are disqualified from testifying]: a brother, a paternal or maternal uncle, a sister's husband, the husband of a paternal or maternal aunt, a step-father, a father-in- law, and a Gis (the husband of his wife's sister):
הן ובניהן וחתניהן וחורגו לבדו
Also, their sons (i.e. of these relatives) and their Chasanim (son-in-laws) are disqualified, and a step-child alone (is disqualified).
א"ר יוסי זו משנת ר' עקיבה אבל משנה ראשונה דודו ובן דודו וכל הראוי ליורשיו וכל הקרוב לו באותה שעה
R. Yosi says, R. Akiva taught this. Mishnah Rishonah disqualified only an uncle, cousin, and anyone proper to inherit him (i.e. paternal relatives), and anyone who was related at the time (that he saw testimony or comes to testify);
היה קרוב ונתרחק כשר
If he was related but became distanced, he is Kosher.
ר' יהודה אומר אפילו מתה בתו ויש לו בנים ממנה הרי זה קרוב:
R. Yehudah says, even if his daughter died and he has children from her, he is a relative [to them].
גמרא מכיון דתנינן אחיו מה צורכה למיתני אחי אביו
(Gemara) Question: Since his brother was taught, why did it need to teach his father's brother? (The Mishnah taught that a brother is Pasul, and also his son (a nephew to his uncle!)
לומר בנו וחתנו של חתן אחי אביו.
Answer: This teaches the son and Chasan of the Chasan of his father's brother. (Hagahos R. Dinar - we infer the repetition (and other repetitions asked below) that the first generation is Pasul to the third, and even through marriages.)
[דף יז עמוד א] מכיון דתנינן אחי אביו מה צורכה למיתני אחי אמו
Question: Since it taught his father's brother, why did it need to teach his mother's brother? (Both of them are a first generation with a second - KORBAN HA'EDAH.)
לומר בנו וחתנו של חתן אחי אמו.
Answer: This teaches the son and Chasan of the Chasan of his mother's brother.
מכיון דתנינן בעל אחותו מה צורכה למיתני בעל אחות אביו
Question: Since it taught [David's] sister's husband, (he is forbidden to David and his son, why did it need to teach the husband of his father's sister? (That is the sister's husband's relation to David's son!)
לומר בנו וחתנו של חתן בעל אחות אביו.
Answer: This teaches the son and Chasan of the Chasan of his father's sister's husband.
מכיון דתנינן בעל אחות אביו מה צורכה למיתני בעל אחות אמו
Question: Since it taught his father' sister's husband, why did it need to teach the husband of his mother's sister? (We already learned that a man is like his wife!)
לומר בנו וחתנו של חתן בעל (אחות) אמו.
Answer: This teaches the son and Chasan of the Chasan of his mother's sister's husband. (I.e. maternal relatives are like paternal, even to make a man like his wife.)
והתנינן חורגו לבדו.
(Mishnah): And a step-child alone. (This implies that a step-daughter's husband is Kosher.)
רב אמר אם חתן חמותו אסור בעל וחרגתו לא כל שכן.
Question (Rav): If the Chasan of his mother-in-law is forbidden, all the more so the husband of his step-daughter! (E.g. if Yakov married Rachel, and each of them has a daughter from a previous marriage, and Reuven and Shimon married those daughters, Shimon is the Chasan of Reuven's mother-in-law, and they are Pasul to each other. All the more so Shimon is Pasul to Yakov!
תיפתר שיש לה בנים וחתנים ממנו.
Answer: The case is, [Rachel] has sons and Chasanim from [Yakov. Then the Chasan of his mother-in-law is his wife's sister' husband (Giso), but the husband of his step-daughter is Kosher.]