Palin's eldest son, Track, and his wife, Britta, welcomed a baby girl named Kyla Grace Palin on Sunday night, reports McGinniss, who moved next door to the Palins's Alaska home in 2010 to gain better access to the family.
In May, it was announced that the high school sweethearts were married. The Palin family never officially confirmed Britta's pregnancy, though pictures of her baby shower surfaced on Facebook.
The former Britta Hanson was once roommates with her husband's younger sister, Bristol, in Anchorage, and served as an executive secretary in the governor's office, beginning when her mother-in-law was governor of Alaska. She is currently a nursing student at the University of Alaska.
Track Palin, an Army Reservist, has said he plans to study at the University of Alaska after the commercial fishing season.
Neither Todd Palin, nor a rep for the Palin family responded to requests for comment.