Question: We should know this because grandchildren are like children, like it says in Yevamos (70a, regarding a Bas Kohen widowed from a Yisrael. She returns to eat Terumah if she has no children.) "We do not need a verse for seed of her seed. Grandchildren are like children."

Answer: There, it is written "v'Zera Ein Lah." "Zera" connotes [even] grandchildren, like it connotes in Sanhedrin (64b) regarding one who passes his son or daughter through fire [to Molech, a rite that is idolatrous or resembles idolatry];

Citation (64b): I would know [that one transgresses] only for his son or daughter. What is the source for the son of his son or the son of his daughter? It says "umi'Zaracha".

Inference: The expression "Zera" connotes [even] grandchildren.

Suggestion: Perhaps there [the Tana] expounds an extra verse!

Rejection: If so, he should have expounded oppositely, for the verse umi'Zaracha is written first.

Distinction: However, "Beno" and "Bito" do not connote to him grandchildren. Therefore, here that it says Ben, we need to include the son and daughter [of the son].

Suggestion: It says "Ervas Ishah u'Bitah Lo Segaleh. Es Bas Benah..." Since it needed to write the son of her daughter, this shows that grandchildren are not like children!

Rejection: We can say that had it not written Bas Benah, we would have forbidden all generations, because grandchildren are like children.

Question: Since grandchildren are not like children, what is the source regarding Yibum that the son's son exempts from Yibum?

Suggestion: We learn from "Ein Lo."

Rejection: We need that to include a Mamzer!

Answer #1: (Indeed, we learn from "Ein Lo.") These Drashos are equally reasonable, so we learn both of them.

Answer #2: We learn the son's son from "Lo Yimcheh" - this excludes [one who left grandchildren], for his name is not wiped out.

Question (Rashba): Why do we need a verse here to teach that grandchildren come before brothers? We should know this, for since regarding Yibum, grandchildren are just like children, also regarding inheritance they are the same!

Answer #1: Here we need to teach that the son's son or the son's daughter inherits with the Mes' [living] sons, or that the daughter's daughter inherits with the Mes' [living] daughters. From Yibum we would know only that [grandchildren] are better than brothers.

Answer #2 (Ri): We learned from inheritance that for Yibum, grandchildren are like children, and not from the reasons I explained above (108a).

Question: What is the source that a Mamzer inherits his father, like it connotes in Kidushin (4a)? Regarding Yibum, we need an inclusion (Yevamos 22b). Also regarding a Bas Kohen, we need an inclusion for Pasul Zera!

Suggestion #1: We learn from "v'Ein Lo", for they [Pasul seed and grandchildren] are equal.

Suggestion #2: The Torah made Yibum dependent on inheritance, and for Yibum there is an inclusion.

Rejection: If we need the Drashah for this, why does it ask in Yevamos (22b) "[a Mamzer] inherits [his father] and becomes Tamei for him [to engage in his burial] - this is obvious!"?

Answer: "Zera" connotes Kosher [seed]. Therefore, regarding a Bas Kohen we need an inclusion. However, "Ben" connotes also Pasul.

Implied question: Regarding Yibum, why do we need to include a Pasul son?

Answer: One might have thought that we learn a Gezeirah Shavah "Achvah-Achvah" from Bnei Yakov. They were Kesherim, and not Pesulim.

Support: Also for this reason, it says there that one might have thought that a Pasul brother does not obligate [the widow] to do Yibum [or Chalitzah], had we not found in a verse that a Pasul son exempts;

Since [a Pasul] exempts (i.e. a Mamzer son, a Pasul) also obligates (a Mamzer brother). See also Tosfos above (109a DH Kivan, who says that we need an inclusion to teach that a Mamzer exempts from Yibum, for through Pasul children, still his name is wiped out).

Explanation: Even if he wants to fix matters for a need at the time, like we find regarding Bnei Binyamin. They enacted that a son's daughter does not inherit with his (her father's) brothers, we do not heed him, due to Tzedukin.

Question (R. Tam): Why did [R. Yochanan ben Zakai] answer [the Tzeduki] from Anah? Perhaps the son's son is like his son, but the son's daughter is not like his son, rather, like his daughter!

Answer (R. Tam): Anah was a woman, like is proven from verses. It says "Eleh Bnei Ahalivamah Bas Anah Bas Tziv'on" - this shows that she was a woman.

Suggestion: Perhaps that was a different Anah!

Rejection #1: It says here that Tziv'on fathered Anah.

Rejection #2: Immediately after the verse brought here, it says "Hu Anah Asher Matza... Eleh Bnei Anah Dishan v'Ahalivamah Bas Anah."

Support: Based on this, R. Yochanan ben Zakai properly answered that the daughter of the son is considered like a son to inherit with the other sons, who precede the daughter, since [Anah] is called "Yoshvei ha'Aretz", and so she is before a daughter. Through this, he refutes their Kal v'Chomer.

Implied question: Why does it say "Hu Anah" in the masculine?

Answer: It is because she inherited with her brother Tziv'on, like a male.

Question: How did Anah inherit? She had a brother, for it says "u'Vnei Tziv'on Ayah v'Anah"!

Answer: Ayah died [before Tziv'on].

Support: It does not list the sons of Ayah, like it lists the sons of Anah.

Explanation #2 (Rashi, on Chumash): Ahalivamah was Bas Anah and Bas Tziv'on. Just like it says here that Tziv'on had Bi'ah with his mother and fathered Anah from her, and therefore [Anah] is listed amidst Bnei Se'ir...

Similarly, Anah had Bi'ah with his mother and fathered Ahalivamah from her. Therefore she is called Ahalivamah Bas Anah Bas Tziv'on. (Bach - "his mother" refers to the wife of Tziv'on (Anah's father). Really, Anah's mother was Tziv'on's mother.)