Jacob, son of Joannes Georg Lambertus and Maria Eva Stoertz, was probably born February 1842 in Waterloo County, Canada West. In the 1901 census the birth was given as 1 February 1842. In the 1911 census the birth was given as February 1844. His obituary indicates he was 82 years old at the time of his death agreeing with the 1842 birth year in the 1901 census.

Jacob married Maria Louisa Rumig, daughter of Joseph Anthony Rumig and Anna Margaretha Heimbacher, on 14 June 1864 at St. Agatha Roman Catholic Church in Waterloo, Waterloo, Canada West. Mary Louisa's husband was given as Jacob Lambertus (from Wellesley) on her death record.The couple had 2 children who were living with Jacob and Jacob's 2nd wife, Natalia, in the 1871 and 1881 censuses:
1 ) Joseph Andrew, born 11 August 1865.
2) John George, born October 1868.

After Mary's death in 1868, Jacob married Natalia Dehler, daughter of George Dehler and Catherine, on 5 July 1870 at St. Agatha Roman Catholic Church in Waterloo, Waterloo, Ontario, Canada.The couple had 12 children:
1) Mary Ann, born 18 December 1870.
2) George William, born 26 April 1872.
3) Emmeline, born 1873.
4) Edward, born 9 April 1875.
5) Albert, born 13 January 1877.
6) Jacob Joseph, born 30 August 1878.
7) Peter, born 30 August 1878.
8) Jacob, born 28 February 1883.
9) Thomas H., born 6 July 1886.
10) Levina Matilda, born 6 July 1887.
11) Robert, born 1890.
12) Natalia A., born 10 March 1892.

Jacob died from heart disease on 1 November 1924 in Teeswater, Bruce, Ontario, Canada. He is buried at Walkerton Cemetery in Walkerton, Bruce, Ontario, Canada. His obituary reads: "Jacob A. Lambertus died suddenly in the Catholic Church in Teeswater on All Saints' Day. The deceased, who was in his 82nd year, belonged to the band of pioneeers who helped clear Brant. Born in Waterloo county, near St. Agatha, he farmed for a time near Bamberg and moved up to the South Line, near Walkerton. Fourteen years ago he purchased the Vendome Hotel at Teeswater. The deceased was twice married, his first wife being Louisa Rumig of Waterloo. Two sons Joseph of Toronto and John G. of Walkerton, survive this union. Five years later, Mr. Lambertus was married to Grotellie[Natalia] Dehler of Waterloo, who survives with a family of three sons and three daughters."
Bio by K. O'Brien