Named for his grandfather, Isaac Moses, Jr. was one nine children born to Joshua and Sarah Rodriguez Brandon Moses. His siblings included twin brother Moses, and brothers Abraham, Israel, Lionel, Benjamin, and Joseph. Isaac was raised in New York and, like his father, he was involved in the East India trade. Isaac and his brother Israel both sought careers in the Unites States Army. Israel, a physician, was appointed assistant surgeon general, stationed with the army first at Vera Cruz and Toluca in Mexico and later at a number of bases in the United States. During the Civil War he was appointed lieutenant colonel of a regiment attached to Sickle’s Brigade and later in the war was responsible for the camp hospitals for the Army of the Potomac. Isaac served as adjutant general of the Third Army Corps of the Army of the Potomac during the Civil War. After the war he spent some time in Galveston, Texas, living there through the yellow fever epidemic to which General Charles Griffin succumbed at Moses’ house. Isaac died unmarried in New York.