According to R. Akiva, "for his brother" teaches that a regular Kohen Gadol, and even a Kohen Gadol Nazir, may be Metamei for a Mes Mitzvah.

Question: Why must the Torah write both "for his father" and "for his mother"? (We ask regarding Nazir and regarding Kohen Gadol.)

Answer: Had the Torah written only "for his father", one might have thought that he may not be Metamei for his father (about whom we are unsure; perhaps his mother became pregnant from another man), for only a Chazakah says that it is his father (most Bi'os of a woman are with her husband);

However, he could be Metamei for his mother, since we know that it is his mother!

Had the Torah written only "for his mother", one might have thought that he may not be Metamei for his mother, because lineage is not traced from the mother, but he could be Metamei for his father, since lineage comes from the father!

The Torah wrote both, to forbid Tum'ah for either of them.

Question: Why do we need "he will not come on any dead souls"?

Answer: "On any" forbids (Tum'ah for) strangers. "Dead" forbids relatives. "Souls" forbids a Revi'is of blood that came from two Mesim.

(Mishnah): A Nazir must shave (Tiglachas Tum'ah) if he became Tamei from any of the following:

A Mes;

A k'Zayis of a Mes;

A k'Zayis of Netzel (this will be explained);

A spoon's worth of a decayed Mes;

A spine and (or) skull;

A limb that separated from the body, in his life or after death, with sufficient flesh on it [that if it were attached to the person, it could heal];

Half a Kav of bones;

Half a Log of blood;

If he touched, moved or was in a tent with any of these, he must shave;

If he touches or moves a bone k'Se'orah (the size of a barley seed), he must shave.

For any of these, he shaves, they sprinkle on him (water with ashes of the red heifer) on days three and seven, and days observed until now are cancelled;

He does not restart Nezirus Taharah until he becomes Tahor. (It is clear from 54a that the words 'and brings Korbanos' must be deleted from the text.)

(Gemara - Beraisa): After R. Meir's death, R. Yehudah told his Talmidim 'don't let Talmidim of R. Meir into the Beis Medrash. They don't want to learn, they just want to refute me.'

Sumchus pushed his way in and said 'R. Meir taught that a Nazir must shave for the following - a Mes; a k'Zayis of a Mes...'

R. Yehudah (angrily): Why did you let him in?! You see he is just causing problems! If a Nazir shaves for a k'Zayis of a Mes, there is no need to teach a (full) Mes!