While there are still many mysteries surrounding the life of James Slavens-- what was his middle name, when did he die, where was he buried-- the biggest mystery is "where does he fit in the Slavens family line?"
It is generally accepted that James is the son of Isaiah Slavens, grandson of John Slaven of County Tyrone. However, the majority of the gedcoms/family group sheets list 1818 as the birth date for James, making him a twin of Phillip. However, this is much too late of a date to be in line with his marriage in 1829 and fatherhood in 1830.
So far, no documents have turned up to pinpoint an earlier date of birth. One source lists James's age at death as 44. Working backwards from 1851, this results in a birth date in 1806 or 1807. The same source puts his death in 1852, though, so it's probably based on recollection-- but we'll add 1808 as a possible birth year to be safe.
The 1850 census lists James's age as 45, which would give an 1804 or 1805 birth date. Of course, we know the reliability of census records, and it's quite possible a handwritten "43" was mistaken for "45" when transcribed. After all, the transcriber mistook "Harvey" for "Henry."
If we place James's birth in 1804-8, how does that fit in with the generally accepted data for Isaiah's other children? Pretty well, actually. Isaiah married Barbara Perks Leaton 13 May 1805, and their first child Benjamin Luther was born in 1806. Benjamin's birth year is reasonable certain, based on a Civil War pension made when he was 77. Then, according to the standard pedigree, there's a gap in births until Mary (Polly) was born in 1812.
Looking at the 1810 and 1820 census returns for Isaiah Slavens is interesting but inconclusive. In 1810, the household is listed as containing four boys under 10 years old, which would fit if they were Hiram, Benjamin, and James, and stepson John Leaton. In 1820 there's only three boys 10-16, which fits Benjamin, James, and John Leaton.
More interesting is the "males under 10" category for Isaiah's household in 1820. It states that there are three males under 10, while the "standard genealogy" states that there are four: Isaiah Jr., Daniel, James, and Philip. There are several documents that suggest that "Isaiah Jr." was James Isaiah Slavens. If we consider that Isaiah Jr. and the "traditional" James are the same person, then the census works out.
Evidence points to James being closer to Benjamin than to other siblings. Voter lists for Hendricks County show that James, Benjamin, and Isaiah all lived in Eel River Township in 1831-2. Benjamin married in Hendricks County, and while he was enumerated in southwestern Boone County in 1830, he voted in Eel River Township through most of the 1830's. Benjamin was the only sibling to purchase items at the public sale following James's death, and he named his son born in 1852 James Harvey Slavens-- perhaps in honor of his recently-deceased brother? While all of this is circumstantial, it helps tie James and Benjamin. Most of Isaiah's other children lived 20+ miles away in Putnam County.
As mentioned, Isaiah is generally accepted as James's father. However, it should be noted that there is one source that names Isaiah's son Reuben as his father. In a 1912 county history biography for Jesse Slavens, it says
"...the son of James and Mary (Davis) Slavens. The Slavens family were a family of soldiers. Many of the Indiana family served in the Mexican War. Reuben Slavens, the grandfather of Jesse and his son Thomas, took an active part in the War of 1812, and Reuben's father served in the Virginia troops in the Revolution..."
The entry is puzzling on several levels; at face value, it states that Reuben Slavens, not Isaiah, was Jesse's grandfather (and therefore James's father). Several facts are correct: Thomas Slavens was a fifer in the War of 1812, and Reuben's father (Isaiah) was indeed a Revolutionary War soldier. However, I've not found any evidence that Reuben was a veteran of the War of 1812; also, Thomas would have been Reuben's brother, not his son (although Reuben did have a son Thomas, he was born much too late to have been a soldier in the war). If you change "Reuben" to "Isaiah" in the quote above, the facts fall into place, as Isaiah's father John was also a Revolutionary War veteran.
So this contradictory information must be taken with a large grain of salt. As many know, county history biographies often contain errors and exaggerations. Jesse may not have had much input on his entry; the book was published after his death, and even if the entry was written a year earlier when he was still living, Jesse was aged and in ill health. His daughter's name is incorrect in the bio, so the credit to Reuben as his grandfather may have been an error or misinterpretation by the entry's author or editor. (Another issue with the county history bio is that "Many...served in the Mexican War." I have not found evidence that this is true; however, many Slavens family members served in the Civil War-- several coming back to Indiana from Missouri to do so! But government records do not show any Indiana Slavenses as Mexican War veterans.)
To cast further doubts on the county history bio, genealogical material passed down through Jesse's family states that Isaiah was the father of James. This material correctly notes that Isaiah had 17 children, but only one brother is mentioned by name: Hiram. It's worth noting that Hiram would have been next closest in age to James after Benjamin, approximately five years older than James. Perhaps James, Benjamin, and Hiram had closer brotherly ties to each other than to older or younger siblings.
Someday maybe a new document will surface, an old Bible will resurface (or undergo the infared photographic process that brings out faded writing), or a long-last cousin with a cache of family mementos will turn up to answer the question of James Slavens's parentage without a doubt. Until then, we'll pencil "Isaiah and Barbara Perks Leaton Slavens" and "1804-1807" as parents and birthdate into our family group sheets.