Son of Daniel Haymore Jr. and Martha Hall. As a young man he heard the Mormon Elders preach and was converted and baptized into L.D.S. Church. Met Adaline Taylor who, along with her father and mother had also been converted to the L.D.S. Church. Emigrated to Utah and married Adaline. Married another wife Elizabeth Ann Lant on March 22, 1888 (later separated and she remarried). In an effort to evade authorities filled an L.D.S. mission to the Southern States and later moved to an L.D.S. colony in Mexico because of polygamy. Sent for Elizabeth to join him. While there his first wife Adaline died and and soon thereafter he married Pearl Wilson Brown. After Pearl's death married her sister Mazie Wilson Cluff.

In 1890 L.D.S. President Wilford Woodruff issued the Manifesto which ended the future practice of Polygamy. The pressure on former polygamous families was reduced. Franklin decided to give himself up went back to Utah in 1893. He was let off with a sentence of one day in the State Penitentiary, which was waived.

Elizabeth was left in Mexico with enough provisions to last her for two years, but she became very discouraged, homesick and bitter after Franklin D. had departed for Utah. She gave most of her belongings away and returned to Payson with two small children, leaving one buried in Mexico, and expecting another one. Franklin moved her to a home in Mapleton, Utah where she gave birth to a son, John Lester, on the 5th of August, 1894. Elizabeth Ann being a second wife had lived on the underground for sometime because the saints were persecuted for living polygamy. For a long time she and her children went by the name of Thane. When the children were first told that their name was not Thane but Haymore, it embarrassed them to start telling people that their name was not Thane, but Haymore.

After the birth of John Lester Haymore in Mapleton in 1894 Lizzie was bitter about polygamy and was very unhappy in her marriage to Franklin D. When he offered to take her back to Mexico in 1895, she declined. She met an older English bachelor, Andrew Crump. She was 26 and he was 39. They were married in Spanish Fork on 8 Nov 1895. They had a son Daniel Wesley Crump, who was born in Spanish Fork on 18 September 1896. Elizabeth Ann died in childbirth with her 6th child on 12 April 1898, and the child died also. Elizabeth Ann Lant Haymore Crump is buried next to Andrew Crump in the Spanish Fork Cemetery.

After war broke out in Mexico Franklin and his families moved to Douglas, Arizona.

Source: History of Franklin Demarcus Haymore by Mildred Adaline Haymore Lewis also from book The Haymore Family, F. Lant Haymore Interview with Minnie Tanner).