Jacob is a nephew rather than a son of Marcus Alexander. (In 1900, 1910 and 1920, this Jacob Alexander was listed in the census as being single and is living with, and a cousin, Bernard Alexander the lawyer.)

Date of birth unclear:
- 1900 U.S. Census, says Mar 1874
- 1910 U.S. Census unclear. May be 1880 or 1890 (age 20 or 30)
- 1920 U.S. Census says c. 1876

1900 U.S. Census says that Jacob immigrated in 1892, yet other information says he came in 1884 aboard the Werra

He possibly died 1940, June 6, Bronx #5622
- born c. 1874
- Single
- worked in boys clothing (cousin of Bernard worked in clothing according to 1920 U.S. Census)
- address: 330 E. 158 Street
- born Hungary
- arrived U.S. c. 1893 (does not exactly match 1884 arrival on the Werra)
- Parents: Marcus Alexander and Yettie Cohen
- burial Montifiore Cemetery Gate 570/N, Block 5, Row 002$, Grave 1, Section 3, Plot 18 (same block as Bernard Alexnder and Selma Weiss Alexander).
- place of death: "Home Hospital of Daughters of Jacob" which is the address listed for this gentleman in the 1940 US Census.