Francis Johnson Webb is known for the novel, The Garies and Their Friends (1857) published in London with the enthusiastic support of Harriet Beecher Stowe, and portraying the lives of free Blacks in the Northern United States prior to the Civil War. 
The Webb family
Frank J Johnson was born 21st of March, 1828, in Philadelphia, Pennsylvania. He
was the youngest child born to Louisa Burr and Francis Webb. Louisa was thought of as "mulatto" since her father, Aaron Burr, third vice president of the U.S., was white and her mother was black. Frank's father was an illustrious member of the Black community of Philadelphia, who lent support to The Haytien Emigration Society, and whose dreams were dashed after the attempt to make a new life in Haiti failed, in 1826. 
Marriages and children
Frank married first Mary Espartero about 1846, probably in Philadelphia. They had no children. A few years after Mary's death in 1859, Frank married Mary Rosabelle Rodgers, with whom he had six children:
Frank Rodgers , born 1865 in Kingston, Jamaica; 
Evangeline Maria Louisa, born 1867 in Kingston, Jamaica; 
Ruth Mary Rosabelle (twin), born 1869, Kingston, Jamaica; 
Clarissa Madeline (twin), born 1869, Kingston, Jamaica; 
Literature & Travels
Frank's first wife, Mary E.Webb, gave public readings of works by renowned authors and made a great impression, so much so that she toured in England, accompanied by her husband, on the recommendation of Harriet Beecher Stowe.  A London editor was subsequently convinced to publish Francis' novel, "The Garies and their Friends" in 1857. Harriet Beecher Stowe played an important role in promoting Frank Webb's novel; she took it upon herself to write an introduction, despite grieving the loss of a son at the time. The novel was not published in the U.S. until 1969. 
By the end of the tour Mary's health took a turn for the worse. Frank accepted a job at the post office in Jamaica, hoping the warm climate would be beneficial for his wife's health. Also, as suggested by author Mary Maillard, it's possible that deep down he hoped life might be better outside the United States. 
Excerpt from "The Garies and Their Friends" :
"[Mr. Winston] decided on leaving the United States, and on going to some country where, if he must struggle in life, he might do it without the additional embarrassments that would be thrown in his way in his native land, solely because he belonged to an oppressed race."
Mary E. Webb succumbed to tuberculosis in 1859. 
Frank stayed on in Jamaica, kept his job and also became a planter. By and by he married a second time. Mary Rosabelle Rodgers was the daughter of a merchant, Thomas Rodgers. Four children were born in Jamaica. 
Return to the United States
About 1870 Frank returned the the U.S., to Washington D.C. where he shared a home with his niece, Sarah Iredell Fleetwood, while "clerking in the Freedmen’s Bureau, and contributing to Frederick Douglass’s New Era"  While in D.C he published a tale in The New Era, titled "Two Wolves and a Lamb". 
It looks like Mary Rosabelle and the children were reunited with Frank in 1872.  Ultimately the family settled in Texas, where the two youngest children were born. 
... the Webbs moved to Galveston, Texas, which had developed a vibrant black community after the Civil War. In 1876, Webb served as an alternative delegate to the Republican state convention.
Webb worked in Galveston first as a newspaper editor, then as a postal clerk, and finally for thirteen years as principal of the Barnes Institute, a segregated school for "colored children".
Frank J Webb, Mulatto, Male, 51, Store clerk, born in Pennsylvania
Mary A. Webb, Mulatto, Female, 34, Wife, born in Jamaica
Frank R Webb, Mulatto, M, 14, Son, born in Jamaica
Evangeline, Mulatto, F, 13, daughter, scholar, born in Jamaica
Ruth M.A., Mulatto, F, 12, daughter, scholar,born in Jamaica
Clarissa, Mulatto, F, 11, daughter, scholar, born in Jamaica
Ethelind, Mulatto, F, 5, daughter, born in Texas
Thomas A, Mulatto, Male, 2, son, born in Texas
Rodgers, Sarah A., Mulatto, F, 28, sister-in-law, born in Jamaica
Rodgers, August K, Mulatto, M, 30, brother-in-law, born in Jamaica
Frank passed away in May of 1894.
"Whereas, it has pleased the hand of Divine Providence to remove from our midst our late worthy and honored principal, Frank Johnson Webb, therefore be it resolved, that we, the teachers of the west district school, deeply deplore the death of one who was in every way worthy of our esteem and regard..." 
He was buried in the Lakeview Cemetery, that is located in Galveston, Galveston County, Texas. 
↑ 3.03.13.23.33.43.5 Mary Maillard. “Faithfully Drawn from Real Life”: Autobiographical Elements in Frank J. Webb’s The Garies and Their Friends, pp 264, 288, 290-291. PENNSYLVANIA MAGAZINE OF HISTORY AND BIOGRAPHY, Vol. CXXXVII, No. 3 ( July 2013)
↑ "Jamaica, Church of England Parish Register Transcripts, 1664-1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:VH68-Z3F : 16 August 2019), Mary Rosabel in entry for Frank Rodgers Webb, 05 Nov 1865, Christening; citing p. 201, Kingston, Jamaica, Registrar General's Department, Spanish Town; FHL microfilm 1,291,766.
↑ 5.05.15.25.220.127.116.11.75.8 "United States Census, 1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MFF1-MJW : 15 July 2017), Frank J Webb, Columbus, Colorado, Texas, United States; citing enumeration district ED 46, sheet 319B, NARA microfilm publication T9 (Washington, D.C.: National Archives and Records Administration, n.d.), FHL microfilm 1,255,297.
↑ "Jamaica, Church of England Parish Register Transcripts, 1664-1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:VH68-ZCZ : 16 August 2019), Mary Rosabelle Webb in entry for Evangeline Maria Louisa Webb, 08 Aug 1867, Christening; citing p. 12, Kingston, Jamaica, Registrar General's Department, Spanish Town; FHL microfilm 1,291,767.
↑ "Jamaica, Church of England Parish Register Transcripts, 1664-1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:VH68-P2P : 16 August 2019), Mary Rosabelle in entry for Clarice Madeline Webbe, 07 Oct 1869, Christening; citing p. 138, Kingston, Jamaica, Registrar General's Department, Spanish Town; FHL microfilm 1,291,767.
↑ Webb, F.J. "Biographical Sketch of Mary E. Webb", Published online by Stephen Railton, Institute for Advanced Technology in the Humanities; Charlottesville, Virginia, 2003. (http://utc.iath.virginia.edu/uncletom/xianslav/xsesfjwat.html: accessed 19 Aug 2020) Originally published in 1856 by Sampson, Low, Son and Co., London.
↑ Frank J. Webb. "Two Wolves and a Lamb", published in The New Era, (Washington, D.C.) 13 Jan 1870, p 4.
↑ "Louisiana, New Orleans Passenger Lists, 1820-1945," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:QKNP-L9MV : 19 August 2020), Mary R Webb, 1872; citing Ship Moses Rogers, affiliate film #057, NARA microfilm publications M259 and T905 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 200,198.
↑ Find a Grave, database and images (accessed 13 July 2020), memorial page for Frank Johnson Webb (21 Mar 1828–7 May 1894), Find A Grave: Memorial #133402300, citing Lakeview Cemetery, Galveston, Galveston County, Texas, USA ; Maintained by Floyd Lanny Martin (contributor 47610184) .