This is definitely an interesting family and it doesnt seem that very many people have worked on them so far. From your post I can see a theme that I have also noticed in my research of the Etheridges: the children often lived with relatives or had informal "adoptions". Not unusual for the time but seems to have occurred several times within this family.
Sarah has took some work to tack down but here is where I am at so far:
William Etheridge m.Lucretia Cripps Nov.23,1854,Dekalb Co.TN
(Not sure when William died but it was after 1860 since he is listed on Dekalb census.)
2.Sarah Etheridge b.1845-1846
1860 Census-Listed in David C.Taylor's household as Sarah Taylor
1860 Census-Listed in her uncle Wilie Hendrixson's household as Sarah Etherage
Sarah m. Jeremiah Hendrixson Oct.6,1861, Dekalb Co., she gives her maiden name as Taylor
She has about 5 children with Jeremiah:George,Cynthia J.,Henry,William H.,and Harriet Lavina Hendrixson
Sarah m.Francis M. Ethridge Jan.24,1873, Dekalb Co., she gives her name as Sarah Hendrixson
It appears my 3rd great-grandmother is their only child, Lucretia, b.Mar.1874
We arent done yet! Sarah marries a final time to Henry H.Cripps on Sept. 11,1875 Dekalb Co., giving her name as Sarah Etherage. Henry is a brother to her stepmother,Lucretia Cripps. I dont know what happened with her marriage to Francis Etheridge because the only Francis Etheridge I could find was born 1855 and is married to another woman by the time 1880 census came around. So that is very intriguing to me. Sarah has 2 children with Henry Cripps: James K.Polk and Amanda Nancy Cripps. They moved to Nashville,Davidson Co.TN where she died in 1916.
3.Lucretia Etheridge(1874-1911) seems to have been adopted by her stepfather, Henry Cripps. She gave her name as Lucretia Cripps when she got married in Nashville and that is what my grandfather always thought her name was. I believe one of her half-sisters also gave Cripps as maiden name instead of Hendrixson.
I plan to work some more on this as I get time. Good to hear from you! (I'm also posting this to genforum)