The people of Zarahemla are often referred to as "the Mulekites." Although this term is not used in the Book of Mormon, Mulek was the son of Zedekiah who accompanied his people to the promised land, and his descendants were the people of Zarahemla. It is useful to review the history of Zedekiah, his sons, and Mulek's people.
First of all, Lehi and his family had left Jerusalem around the first year of Zedekiah's reign. Mulek and his people left at the end of Zedekiah's reign, about 11 years later. What happened to Zedekiah before he was taken to Babylon is both gruesome and interesting. The Chaldeans' army…overtook Zedekiah in the plains of Jericho…Then the king of Babylon slew the sons of Zedekiah in Riblah before his eyes: also the king of Babylon slew all the nobles of Judah. Moreover he put out Zedekiah's eyes, and bound him with chains, to carry him to Babylon (Jer 39:5-7). Zedekiah was kept in prison until the day of his death (Jer 52:11).
The obvious question, then, is how could Mulek have come to the Americas if he was a son of Zedekiah? The record states that the sons were killed in the presence of their father. Apparently, Mulek was somehow spared from this ignominious demise, And now will you dispute that Jerusalem was destroyed? Will ye say that the sons of Zedekiah were not slain, all except it were Mulek? Yea and do ye not behold that the seed of Zedekiah are with us, and they were driven out of the land of Jerusalem? (Hel 8:21).
Hugh Nibley
"Nowhere are we told that Mulek was the leader of the company, and indeed at his age that would be unthinkable-his father Zedekiah was only about thirty-one when he was taken prisoner and blinded. But as the sole survivor of the royal family and heir presumptive to the throne, he was certainly the most important person in the company, a source of legitimate pride to the group. The name tells everything-'Mulek' is not found anywhere in the Bible, but any student of Semitic languages will instantly recognize it as the best-known form of diminutive or caritative, a term of affection and endearment meaning 'little king.' What could they call the uncrowned child, last of his line, but their little king? And what could they call themselves but Mulekiyah or Mulekites?" (Book of Mormon Authorship: New Light on Ancient Origins, p. 118)
The next important point that this brings up is that the Mulekites must have been of the tribe of Judah. All the kings of Judah, since the reign of king David, were of the tribe of Judah. Our tendency to think of the Nephites as strictly of the tribe of Manasseh is not correct. The Nephites merged with the Mulekites and also had some of the blood of Ishmael (of the tribe of Ephraim) amongst them. Therefore, the Nephites, by the time Christ comes, had the blood of Ephraim, Manasseh, and Judah in their veins.
James E. Talmage
"The Prophet Joseph Smith informed us…that Ishmael was of the lineage of Ephraim, and that his sons married into Lehi's family, and Lehi's sons married Ishmael's daughters…Thus these descendants of Manasseh and Ephraim grew together upon this American continent, with a sprinkling from the house of Judah, from Mulek descended, who left Jerusalem eleven years after Lehi, and founded the colony afterwards known as Zarahemla found by Mosiah -- thus making a combination, an intermixture of Ephraim and Manasseh with the remnants of Judah, and for aught we know, the remnants of some other tribes that might have accompanied Mulek. And such have grown up upon the American continent.' -- From "Discourse by Apostle Erastus Snow," at Logan, Utah, May 6, 1882, see Journal of Discourses, vol. 23, pp. 184, 185." (James E. Talmage, A Study of the Articles of Faith, p.504-5)