Jacob Miller (Sr.) was born about 1735, in modern-day Franklin County (then part of Lancaster County), Pennsylvania. He is held by many to be a son of Michael and Susanna (Berchtol) Miller, although he is not specifically mentioned to be in the "Brethren Encyclopedia." He reportedly first married Barbara Brower in 1761 but she died soon thereafter. He married a woman named Mary or Elizabeth of the Franklin County area and as many as 12 children. Elizabeth died in 1801 and Jacob remarried to Barbara Lybrook the same year.