I am not related.In reviewing the census records for Edgar County, Illinois there is a G. W. Riley shown in the 1840 census as follows: 3 males 20/29; 1 female 0/5, 1 female 10/14, 1 female 20/29 and 1 female 40/49.G. W. was the head of household, his mother is the 1 female 40/49.Thereafter Garrard married to Bethier McClain.
1850 Edgard Co., Ill Garrard W. Riley 36 OH Betherre 37 KY Ninian A. 6 Ill Emeline 10/12 Ill Garrard died in 1881 and Bethier died in 1904.Garrard was a minister and moved from Edgar co., Ill to parts unknown as he cannot be found in 1860.In 1870 he is living in Champaign co., Ill. What is odd is that all the family public trees I have found show Garrard and Bethier as having 3 children only.Yet in 1900 Bethier lives part of the time with son Ninian and states 7 children with 2 living. The rest of the time with son Ozias and again she states 7 children with 2 living. If Jennie was one of the children she was deceased prior to 1900 and would have been one of the 5 children deceased by 1900.
In 1880 Jennie shows her father as born in Kentucky and mother as born in Ohio. It is possible that Garrard born Ohio and Bethier born in KY were her parents and she just had their places of birth turned around.
Mary Ann Riley 1800 KY - 8/1879 Ill was married to Ensign Mitchell 2/21/1850.I could find no marriage record prior to 1850 for a Mary Ann Unknown marrying a Riley so I do not know what her husband's name was or who her children were, if she had any.It is possible that Mary Ann was Jennie's grandmother but then again given the ages of Ensign and Mary Ann, Jennie might have been left to take care of them while her family moved away, it was common practice to leave a child to care for the elderly and Mary Ann was probably related somehow.Both of her brothers married (Ninian and Ozias) married prior to 1870 as did Jennie, if they were her brothers.
I found it odd that Jennie is shown marrying 7/22/1865 to a George Brown not a George Miller.Jennie died in Iowa after 1880 before 1900, in 1880 they are living in Franklin County, IA.So it is possible that there is an obituary that may give you some answers like living siblings who could be tracked back.In 1900 husband George is living in Sioux Co., IA with Etta M. Kellog and in 1910 he is living in Cherry Co., Nebraska with Albina Cramer, his daughters.
Garrard Riley died in 1881 in Champaign, Ill and wife Bethier died in 1904.
I know this gives you no solid answers but a look-see for an obituary may give you the answers you are looking for.I could not find a marriage record for a Robert Riley and Elizabeth Gordon.Additionally, I could not find a Robert Riley or an Elizabeth Gordon residing in Edgar in 1850, just one year prior to Jennie's birth and since she was born in June 1851 they should have shown on the census.
Good luck in your search, the above is food for thought.