When Bill Griffeth’s cousin asked him to take a DNA test a few years ago, he never would have guessed that his life would be changed forever.

Griffeth is a TV news anchor on CNBC, and he serves as a Trustee of the New England Historic Genealogical Society in Boston, so he understood why his cousin enjoyed researching their family history: He loves genealogy, too.

But nothing in his career as a veteran professional journalist or amateur genealogist prepared him for what that DNA test revealed: that his father was not his biological father.

All sorts of thoughts raced through his head: Could his mother have had an affair? No way. Perhaps the test results were wrong.

“My life wasn’t altered by an act of God. Instead, it was changed by the revelation of a deep dark family secret that, like a time bomb, had been ticking my whole life,’’ Griffeth writes in his new book, “The Stranger in My Genes,’’ a gripping memoir that chronicles the aftermath of learning this news, his search for his biological father, and the impact it had upon him and his family.

The memoir is available in hardcover and e-book format from the New England Historic Genealogical Society’s online store at www.americanancestors.org/store.