Union war dead and relatives

Inscribed monuments tell us stuff, but not everything. The War for Union/ War for Southern Secession sent corpses to the majority of then extant graveyards in the country. Some monuments were for groups and listed the dead for that unit. They all did not come to that site.

Some bodies were misidentified. Some were moved and reburied. Some bodies were not found, and the marker is a cenotaph [from the Greek for empty tomb]. This does not just go for war dead, not everyone is buried under their real name. Some times the dates, or other information is wrong or puzzling. Just something to keep in mind.
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Frederick Scarr died at Shiloh, Tennessee. The battles were fought 6 and 7 April 1862. Shiloh was the deadliest American battle to that point in time. The war would go on for three more years. Grant would no longer think one big battle will decide the war. Frederick is listed as dying there in May. Did he die of wounds and or illness? He was twenty.
James Scarr was eighteen when he died at Kinston, North Carolina on March 18, 1865. The second largest battle fought in North Carolina was at Wyse Fork from 7 to 10 March. Both are in Lenoir County, Kinston is the county seat. Lee would surrender on the 9th of April. James had been dead for three weeks.

James' father died in 1854. The next day his 2 yr old brother died. His mother re-married, and died in 1862. His half-sister died at 5 days of age in 1860.

Frederick's father was twenty years older than James' father. Were they brothers, or father and son. Was Frederick's father uncle, or grandfather to James?