Mormon gives us a little more biographical information. He is named after his father, and he is “a descendant of Nephi.” It is assumed that he meant the first Nephi, son of Lehi. However, he does not say so, and it is possible that he meant the Nephi, son of Nephi, who was a disciple of Christ. Mormon was also a disciple (the Book of Mormon term for apostle), and that would make a connection to the more recent Nephi an intriguing possibility. Coming nearly a thousand years after Nephi, son of Lehi, it would be impossible to have a completely accurate genealogy, and would indicate a general connection rather than a literal direct descendent.
Mormon is taken south to Zarahemla. Zarahemla had been rebuilt after having been burned in the destruction preceding Christ’s appearance in Bountiful. It would appear that the center of Nephite government had been relocated to the more northern lands (and probably Bountiful). Thus Mormon (his father), took Mormon south. The reason appears to be a war between Nephites and Lamanites. It would appear that both Mormon and his father were part of a warrior culture, if not a warrior caste. His father would likely be in charge of at least some of the armies. Mormon (the son) would later also assume command.
Importantly, we have the definitions of Nephite and Lamanite again according to the traditional tribal affiliations. These were reconstituted after there were no such divisions. See the commentary for 4 Nephi 1:38.