For 145 years, some have maintained that John Wilkes Booth was not the man cornered and shot in a Virginia barn 12 days after the crime.
The family hopes DNA comparisons will tell whether the story of Booth's flight is true, The Philadelphia Inquirer reports.
"I'm absolutely in favor of exhuming Edwin," said Joanne Hulme, of Philadelphia, the historian in the Booth family. "Let's have the truth and put this thing to rest."
Efforts to open the Baltimore grave believed to be John Wilkes Booth's were blocked in 1995 by a judge who said its location could not be definitely determined. The family had hoped to use the skull, along with scars, to make an identification.
The best option now is to compare DNA from Edwin Booth, buried in Cambridge, Mass., with a specimen from the man shot at the barn, who experts agree is buried in Baltimore.
According to one theory, Booth escaped to live in Texas as John St. Helen, then changed his name to David George and moved to what is now Oklahoma before poisoning himself.