Question: When was John Slater elder brother born? 

Context articles: The Rhode Island System
Jacqueline Left Hand Bull
John Slater (industrialist)
Cameron Slater
Samuel Slater
Slater family
William Slater (cricketer)
Rob Slater
Eva Slater
Baron Blayney

The Rhode Island System refers to a system of mills, complete with small villages and farms, ponds, dams, and spillways first developed by Samuel Slater and his brother John Slater (brother Samuel Slater, who had earlier built the first fully functional water-powered textile mill in America at Pawtucket, Rhode Island, in 1790.
Jacqueline Left Hand Bull (formerly Delahunt, born in 1943), member of the Sicangu Lakota of the Rosebud Sioux Tribe, was brought up in her view in a traditional Lakota way by her grandparents and parents.
 She became a member of the Bahá'í Faith in 1981, appointed a Continental Counselor in 1988, and was elected as Chair of the National Spiritual Assembly of the Bahá'ís of the United States in 2007.
 The family history of the name "Left Hand Bull" involves the elder brother of a family who had done the difficult task of hunting a Buffalo from the left side and was known to provide for more than his family in his hunting.
 Years later the younger brother reconnected with the elder and undertook to greatly honor the elder in a ceremony and in return the elder brother traded his name.
 She shares a short stature with this younger brother who was given the name "Left Hand Bull".
John Slater (December 25, 1776–1843) was an early American industrialist, founder of Slatersville, Rhode Island and younger brother of Samuel Slater, father of the American Industrial Revolution, and a member of the well-known Slater family.
Cameron Slater, a controversial, right-wing New Zealand-based blogger, is arguably best known for publishing the "Whale Oil Beef Hooked" blog.
 He edited the tabloid newspaper "New Zealand Truth" from November 2012 until it ceased publication in July 2013.
 Slater's father, John Slater, served as President of the New Zealand National Party from 1998 to 2001.
Samuel Slater (June 9, 1768 – April 21, 1835) was an early English-American industrialist known as the "Father of the American Industrial Revolution" (a phrase coined by Andrew Jackson) and the "Father of the American Factory System."
 In the UK, he was called "Slater the Traitor" because he brought British textile technology to America, modifying it for United States use.
 He learned textile machinery as an apprentice to a pioneer in the British industry, then immigrating to the United States at the age of 21.
 He designed the first textile mills in the US and later went into business for himself, developing a family business with his sons.
 A wealthy man, he eventually owned thirteen spinning mills and had developed tenant farms and company towns around his textile mills, such as Slatersville, Rhode Island.
The Slater family is an American philanthropic, political, and manufacturing family from England, Rhode Island, Massachusetts, and Connecticut whose members include the "Father of the American Industrial Revolution," Samuel Slater, a prominent textile tycoon who founded America's first textile mill, Slater Mill (1790), and with his brother John Slater founded Slatersville, Rhode Island in North Smithfield, Rhode Island in 1803, America's first planned mill village.
 The family includes various merchants, inventors, art patrons, and socialites.
 John Fox Slater, was a prominent abolitionist who founded the Slater Fund and built the historic John F. Slater House and Slater Library.
 William A. Slater was a noted art collector and philanthropist who created the Slater Memorial Museum in Connecticut.
 After moving many of their mills to the South from New England, the village of Slater-Marietta, South Carolina was named after the family.
William Slater (17 November 1790 at Storrington, Sussex – 9 March 1852 at Brighton) was an English professional cricketer.
 His brother was John Slater (1795-unknown), also of Sussex, who played in 7 matches from 1825 to 1829.
Robert John Slater (1960 – August 13, 1995) was an American mountaineer known for his first ascent of the big wall route "Wyoming Sheep Ranch" on El Capitan.
 A tireless outdoor recreationalist, Slater built up an impressive climbing resume during his college years and later as he worked as a trader on the Chicago Board of Trade and for Goldman Sachs.
 He died on August 13, 1995, while descending from the summit of K2.
Eva Slater (June 17, 1922 - May 2, 2011), a Hard-Edge artist was born in Berlin, Germany in 1922 and studied art at the Lotte Art Academy.
 After WW2 ended she moved to the United States where she worked as a fashion illustrator in New York City.
 After meeting her husband, John Slater, they moved to Los Angeles, California where she began studying painting at Art Center College of Design.
 It was there that she met Lorser Feitelson who founded the Los Angeles based Hard Edge art movement.
 Slater became a prominent member of the Hard Edge movement from 1950 through the late 1960s.
Lord Blayney, Baron of Monaghan, in the County of Monaghan, was a title in the Peerage of Ireland.
 It was created in 1621 for the soldier Sir Edward Blayney.
 He was succeeded by his son, the second Baron.
 He was killed at the Battle of Benburb in 1646.
 His younger son, the fourth Baron (who succeeded his elder brother), represented County Monaghan in the Irish House of Commons.
 His elder son, the fifth Baron, was attainted by the Parliament of James II for supporting William of Orange.
 He had no sons and was succeeded by his younger brother, the sixth Baron.
 He was Governor of County Monaghan.
 His son, the seventh Baron, was Lord Lieutenant of County Monaghan.
 He was succeeded by his elder son, the eighth Baron.
 He was a clergyman and served as Dean of Killaloe.
 He had no surviving children and was succeeded by his younger brother, the ninth Baron.
 He was a Lieutenant-General in the Army.
 His younger son, the eleventh Baron (who succeeded his elder brother), was also a Lieutenant-General in the Army and fought in the Peninsular War.
 Lord Blayney also represented the rotten borough of Old Sarum in Parliament.
 His son, the twelfth Baron, sat as Conservative Member of Parliament for County Monaghan and was later an Irish Representative Peer from 1841 until his death.
 On his death in 1874 the title became extinct.