Your research is incorrect and this is what happens when you copy information and don't do your own work. Rachael Sharp was the mother of William, Letitia, Unknown male, Sarah Jane, Douglas William, Horatio, Abigail and Eliza Sinclair. She is not the mother of Joseph, George Washington Jr., Nancy or any other children. George had a relationship with Lucinda Cosby and their first FIVE children were born out of wedlock before George and Nancy married in Orange County in 1836. Joseph Sinclair is not the son of George Washington Sinclair, but the son of William Douglas Sinclair and Ruth Lawrence. Proven by hard documentation. The children of George Sinclair and Lucinda Cosby were James, Thomas, Nancy, George W. Jr., Ransom, John A. H., Letty, Wayman and Margaret.
Divorce in Harrison County, Indiana, Fall Term 1835, Rachael Sharp Sinclair was granted divorce from George Washington Sinclair on the grounds of adultery. The divorce papers state that George and Rachael were married in Wayne County Indiana sometime in the winter of 1808 and they were the parents of eight children. The papers state that in order to protect her inheritance from her father, and due to her poor health, she was giving the four youngest children, Douglas, Horatio, Abigail and Eliza (their ages were stated in the papers), to George and Lucinda to keep and raise. The divorce papers stated that after the birth of Eliza, Rachael threw George out of her bed, and George took up with the maid, Lucinda Cosby, who he kept on their property with their five children that were born out of wedlock. As for Rachael's "poor health", she lived to be 77 years old and died in Orange County, Indiana. Lucinda or George can't be found after the 1850 census since the family is missing on the 1860 census, so it is presumed she died between 1850 and 1870. Several of the youngest children were sent to Putnam and Owen counties to live with relatives, but George was still buying and selling land after 1860 in Orange and Crawford. I have copies of deeds. In the Spring or Summer term of 1835, George Sinclair and Lucinda Cosby were prosecuted in Orange County, Indiana for open and notorious adultery, were found guilty and each fined a large sum of money. They married nearly immediately after George's divorce from Rachael was over, in January 1836.
I went to Orange County to obtain a copy of the 1835 lawsuit, but the County Clerk, Roger Purkhiser, told me that sometime in 2010-2011, when they were moving records from the old courthouse to a new location, an employee took it upon herself to throw Civil Book #1 away along with other records, because she didn't think the records were needed any longer.