The following may be of some help.
From the History of Wapello County-1878, pp. 649-650:
LATHROP, JOEL, farmer, Sec. 26; P.O. Munterville; owns 163 acres of land, valued at $3,300; born in the State of New York in 1801; moved to Indiana in 1833; thence to his present location in 1860. Married in 1822 Margaret Gordon, who died in 1830; had three children none of whom are living; married in 1834 Helen Dickson who died in 1850; had five children, two living-Harrison, born in 1839, and Helen, born in 1844; married for his third wife Maria Godman, born in Ohio in 1812; have one daughter-Emma born in 1851; she had nine children by a former marriage, five living.
Other related informaiton:
Joel Lathrop married Eleanor Dickson 6 Nov 1834 in Tippecanoe County, Indiana
Joel Lathrop married Maira Godman 29 Dec 1850 in Tippecanoe County, Indiana
The following are listed as buried in the Brooks Cemetery, Polk Township, Wapello County, Iowa in the WPA records:
Lathrop, Joel; died 19 Jun 1883 aged 81
Lathrop, Maria; died 16 Dec 1887 aged 75
Lathrop, Nancy E.; born 1847 died 26 Sep 1912
Lathrop, H.T.; born 1839, died 19 Apr 1919
Lathrop, Eva F; born 1879 died 24 Nov 1901
Wapello County marriage records indicate that -
Harrison T. Lathrop married Nancy E. Kerr on 29 Jan 1867
Emma F. Lathrop married Loman Fisk 10 Jan 1871
I find nothing on Martha E. (alias Helen) in the marriage records
Emma and Loman Fisk are last found in Rose Creek Township, Republic County, Kansas in 1880 with children Edmon-aged 5, Bertha-aged 3, and Loman O.- aged 1.