The printer’s manuscript has the singular family whenever the reference is to an individual (the brother of Jared and his family as well as Jared and his family), but the plural families occurs when the text refers to the brother of Jared’s friends and to Jared’s friends. In other words, each individual has one family. Unfortunately, the 1830 compositor accidentally set families when referring to the family of the brother of Jared, probably because his eye caught the plural families in the next line of the printer’s manuscript. There is definitely no intent in the original text to assign more than one family to the brother of Jared; the singular reading of the original text should be restored here, even though the plural reading has caused some controversy. For instance, Orson Pratt, the editor for the 1879 LDS edition, added a footnote here: “From this verse it is seen that the brother of Jared had a plurality of families.” Walter W. Smith, writing in the RLDS publication The Saints’ Herald 56/40 (6 October 1909), draws attention on page 943 to Pratt’s footnote, then concludes with this remark (based on the fact that the 1908 RLDS edition restored the correct singular): “But another error has been corrected, and with it another defense of polygamy is gone.” Richard P. Howard, formerly the RLDS Church Historian, provides a more neutral evaluation of the RLDS perspective on page 41 of his Restoration Scriptures: A Study of Their Textual Development, second edition (Independence, Missouri: Herald Publishing House, 1995):
The acquisition of the P MS [the printer’s manuscript] in 1903 made possible the clarification of a text which in the Reorganization’s historic warfare against polygamy was considered in 1906 to be very important to the cause. Today we would treat such a matter in keeping with its current relative importance, but in the early 1900s few considerations were much more significant.
Here the year 1906 refers to the RLDS committee’s revision of the RLDS text for the third RLDS edition, published in 1908.
Ultimately, this contentious issue in LDS and RLDS church history should play no role in determining the text of the Book of Mormon. Here in Ether 1:41, the critical text will restore the singular family, the reading of the earliest textual source (the printer’s manuscript).
Summary: Restore the original singular family in reference to the brother of Jared in Ether 1:41; the plural reading “thy families” is a typo that was introduced by the 1830 compositor.