The second occurrence of the possessive pronoun his in this sentence seems to be referring to Ammon, yet the first part of the sentence states that not only Ammon but also his men were filled with sorrow over the losses that the people of Limhi had suffered. Joseph Smith’s emendation of the second his to their for the 1837 edition appears to have been an attempt to have the possessive pronoun refer to Ammon and his men. Earlier Ammon specifically refers to the people of Limhi (originally, the people of Zeniff ) as “our brethren”:
Similarly, king Limhi refers to Ammon and his men as “his brethren”:
Although the use in Mosiah 21:29 of his creates a difficult reading, it is possible to interpret the his as referring to Ammon alone. Sometimes the Book of Mormon text will refer to a leader’s individual actions and then in the same passage use the leader’s name to describe the actions of the group he leads, as in the following descriptions regarding the actions of the Nephite general Lehi:
Thus it is possible to interpret Mosiah 21:29 as switching from a reference to the group (“Ammon and his brethren”) to Ammon alone, the leader of the group (“many of his brethren”).
Joseph Smith’s emendation to their suggests a second possibility: the occurrence of his in “many of his brethren” in Mosiah 21:29 may actually be the result of an early scribal error for their in the transmission of the text. For instance, Oliver Cowdery could have accidentally copied an original “many of their brethren” as “many of his brethren” since he had just written “Ammon and his brethren”. It is also possible that such an error could have occurred when the scribe in 𝓞 took down Joseph’s original dictation.
A third possibility is that the earliest reading “many of his brethren” is correct but that the possessive pronoun his actually refers to Limhi rather than Ammon. In other words, the intended meaning of the earliest reading in Mosiah 21:29 is that “Ammon and his brethren were filled with sorrow because so many of his [Limhi’s] brethren had been slain”. Sometimes in the Book of Mormon, the pronominal referent is not the last-mentioned individual; the referent may have occurred some time earlier in the passage, as in the following complex example involving Alma, Amulek, and Zeezrom in the book of Alma:
It is therefore possible that the his in Mosiah 21:29 could be referring to king Limhi. Also note that Limhi himself refers to his own people as “our brethren”, as in the following passage where Limhi is speaking to his people:
Since the pronoun his will work in Mosiah 21:29, the critical text will maintain the earliest reading. The his can refer either to Ammon or to king Limhi himself. But there also remains the possibility that the phrase “many of his brethren” is an error deriving from the previous “Ammon and his brethren”.
Summary: Restore the earliest reading in Mosiah 21:29: “because so many of his brethren had been slain”, where the his may refer to Ammon or to king Limhi; there is also the possibility that this his is an error for their.