Isaac was born in Ekaterinoslav, Russia (now Ukraine). His parents were Chaim Yehudah Pesachinsky, a well-respected rabbi there, and Yetta Shimernitsky.
According to his Declaration of Intention to become a U.S. citizen, he was born March 13, 1879. Conflicting data!
While still in Ekaterinoslav, Isaac met Sonia Belkin, daughter of a successful businessman. She was the oldest of ten children.
(Later, Sonia's youngest sister immigrated to be with her. Nora married Jack Katz, Isaac's nephew. More info.)
Isaac and Sonia's children: