Although little is known about the life of Eleazer, more detail emerges with each subsequent generation of De Youngs. Eleazer was a small merchant who most likely arrived from Holland in the mid-eighteenth century. He settled in Philadelphia and his son Joseph set up a general store in New Hanover Township, Montgomery County, Pennsylvania in the early nineteenth century.

Joseph’s son Philip, born in 1807, moved to Philadelphia at age twenty-seven, where he studied in the medical department of the University of Pennsylvania. Graduating in 1838, he became physician to the Lehigh Navigation Company, though by 1844 he had gone into private practice. Two years later, he married Harriet Esther Souza, daughter of a French Sephardic family who had immigrated to the United States in the 1820s. Philip served on the city’s Board of Health and was active in freemasonry. He earned a reputation as a physician willing and eager to serve the poor.