London (CNN) -- Britain's royal family has long been taunted for its German roots, but now a more exotic lineage can be revealed after evidence emerged indicating that Prince William is the direct descendant of an Indian woman.
The Duke of Cambridge's maternal lineage was revealed on Friday by a genetic ancestry testing company, BritainsDNA, which carried out tests on the DNA of Princess Diana's two matrilineal cousins and compared them to a global database of samples.
Those tests reveal that the prince's fourth great-grandmother was the daughter of Eliza Kewark and Theodore Forbes (1788-1820), a Scottish merchant who worked in Surat, north of what is now Mumbai.
Kewark's mitochondrial DNA -- which is only passed on from mother to child -- was then passed down, the company says, through the couple's daughter and female descendants, one of whom, Frances Roche (1936-2004), married Earl Spencer and bore a daughter, Lady Diana Spencer, the prince's mother.
Jim Wilson, chief scientist at BritainsDNA, told CNN the discovery means "William probably has a very small amount (of Indian DNA), maybe half a percent will be of South Asian heritage."
"The mitochondrial DNA will not be passed on to the child of William and Kate," he added. "But because we also did some testing on the other DNA of his cousins, we could see that they had little bits of Indian DNA across their genome, so it's quite likely that William has a few other bits of Indian DNA, and he could well pass them on to the child."
Prince William's wife, Catherine, the Duchess of Cambridge, is expecting the couple's first child.
Buckingham Palace declined to comment.