On 14 Aug 1720 Frederick Hesse-Kassel was born to William Hesse-Kassel (age 38) at Kassel.

On 08 May 1740 Frederick Hesse-Kassel (age 19) and Mary Hanover (age 17) were married. She the daughter of King George II (age 56). She the daughter of King George II of Great Britain and Ireland and Caroline Hohenzollern Queen Consort England. He the son of William Hesse-Kassel (age 58). They were fourth cousins.

On 25 Dec 1741 [his son] William Hesse-Kassel was born to Frederick Hesse-Kassel (age 21) and [his wife] Mary Hanover (age 18). He a grandson of King George II of Great Britain and Ireland.

On 03 Jun 1743 [his son] William Elector of Hesse was born to Frederick Hesse-Kassel (age 22) and [his wife] Mary Hanover (age 20). He a grandson of King George II of Great Britain and Ireland.

On 11 Dec 1743 Frederick V King Denmark and Norway (age 20) and [his sister-in-law] Louise Hanover Queen Consort Denmark and Norway (age 18) were married. She by marriage Queen Consort Denmark and Norway. She the daughter of [his father-in-law] King George II of Great Britain and Ireland (age 60) and Caroline Hohenzollern Queen Consort England. He the son of Christian VI King Denmark and Norway (age 44). They were third cousin once removed.

On 19 Dec 1744 [his son] Charles Hesse-Kassel was born to Frederick Hesse-Kassel (age 24) and [his wife] Mary Hanover (age 21) at Kassel. He a grandson of King George II of Great Britain and Ireland.

On 11 Sep 1747 [his son] Frederick Hesse-Kassel was born to Frederick Hesse-Kassel (age 27) and [his wife] Mary Hanover (age 24). He a grandson of King George II of Great Britain and Ireland.

On 31 Mar 1751 [his brother-in-law] Frederick Louis Hanover Prince of Wales (age 44) died at Leicester House.

On 19 Dec 1751 [his sister-in-law] Louise Hanover Queen Consort Denmark and Norway (age 27) died.

On 01 Feb 1760 [his father] William Hesse-Kassel (age 77) died. His son Frederick Hesse-Kassel (age 39) succeeded II Landgrave Hesse Kassel. [his wife] Mary Hanover (age 36) by marriage Landgravine Hesse Kassel.

On 01 Sep 1764 [his son] William Elector of Hesse (age 21) and [his daughter-in-law] Electress Wilhelmina Caroline Oldenburg (age 17) were married at Christiansborg Castle. She the daughter of Frederick V King Denmark and Norway (age 41) and [his sister-in-law] Louise Hanover Queen Consort Denmark and Norway. He the son of Frederick Hesse-Kassel (age 44) and [his wife] Mary Hanover (age 41). They were first cousins. He a grandson of King George II of Great Britain and Ireland. She a granddaughter of King George II of Great Britain and Ireland.

On 31 Oct 1765 [his brother-in-law] William Augustus Hanover 1st Duke Cumberland (age 44) died unmarried. Duke Cumberland extinct. He was buried at King Henry VII Chapel, Westminster Abbey [Map].

On 30 Aug 1766 [his son] Charles Hesse-Kassel (age 21) and [his daughter-in-law] Louise Oldenburg (age 16) were married at Christiansborg Castle. She the daughter of Frederick V King Denmark and Norway and [his sister-in-law] Louise Hanover Queen Consort Denmark and Norway. He the son of Frederick Hesse-Kassel (age 46) and [his wife] Mary Hanover (age 43). They were first cousins. He a grandson of King George II of Great Britain and Ireland. She a granddaughter of King George II of Great Britain and Ireland.

On 14 Jan 1772 [his wife] Mary Hanover (age 48) died.

On 10 Jan 1773 Frederick Hesse-Kassel (age 52) and Princess Philippine Hohenzollern (age 27) were married. No issue. The difference in their ages was 25 years. He the son of William Hesse-Kassel. They were third cousins. She a great granddaughter of King George I of Great Britain and Ireland.

On 31 Oct 1785 Frederick Hesse-Kassel (age 65) died. His son [his son] William Elector of Hesse (age 42) succeeded IX Landgrave Hesse Kassel. [his daughter-in-law] Electress Wilhelmina Caroline Oldenburg (age 38) by marriage Landgravine Hesse Kassel.

On 01 May 1800 [his former wife] Princess Philippine Hohenzollern (age 54) died.