JOEL - Ephraim was given the birthright and is therefore the presiding tribe. The tribe of Manasseh does everything Ephraim does, except the responsibility of leadership in conducting the work of God, but both tribes take precedence over all the other tribes and will both administer salvation to the whole House of Israel in the last days.
The Nephites were from the blood of Manasseh. Many members of the Church are of the tribe of Manasseh. In Mexico and mid and South America 60 to 90% of all members given patriarchal blessings are identified as being of the tribe of Manasseh.

BONNIE - Thanks for your response. Can you tell me where in the scriptures this information can be found?

JOEL - In the Joseph Smith translation of Genesis 48:9, speaking about Ephraim and Manasseh, Jacob tells their father Joseph that his two sons will preside over the other tribes:

9. "In delivering my people, thy brethren, from famine which was sore in the land; wherefore the God of thy fathers shall bless thee, and the fruit of thy loins, that they shall be blessed above thy brethren, and above thy father’s house;
10 For thou hast prevailed, and thy father’s house hath bowed down unto thee, even as it was shown unto thee, before thou wast sold into Egypt by the hands of they brethren; wherefore thy brethren shall bow down unto thee, from generation to generation, unto the fruit of thy loins for ever;
11 For thou shalt be a light unto my people, to deliver them in the days of their captivity, from bondage; and to bring salvation unto them, when they are altogether bowed down under sin.

Gen. 48:14-20 explains how Ephraim was chosen over the older Manasseh to have the birthright.