He was the son of Jacob Peck, who had immigrated to America in 1740. His father's last name was originally Bach, and when he arrived in America, he changed it to Back, and then to Beck. His father's last name later became Peck, and all of his children, including Jacob Jr., had the last name of Peck.
Jacob Jr. first married Margaret Kingery, on June 20, 1795. They had about fourteen children, but only the names of six have been confirmed: Mary Ann (born 10-15-1800); Jacob (born about 1805); Abraham (born 1811); Isaac (born 1812); Louis (born 11-7-1816); Joseph (born 1819); and George Washington (born 2-19-1819).
Jacob Jr.'s first wife died around 1824, and he got remarried to Julia Ann Litz Romans, around 1825. She was also a widow. She was previously married to Joshua Romans and they had at least seven children. They had lived along Copper Creek, but he had died around 1824.
Jacob had at least five children with Julia: Martin (born 1829); twins, Benjamin Fairchild and Leonard Litz (born June 15, 1830); James J. (born June 17, 1832); and Henry (born April 23, 1835).
Jacob Jr. died around 1843, and his second wife Julia died in 1845. Their two youngest sons, James and Henry, then moved in with Julia's brother, Peter Gose Litz, who lived on the old Litz family farm in Burke's Garden, Virgina (in Tazewell County).