Anthony McPartlin and Declan Donnelly embark on a journey to New York to follow the bloodlines of their mothers using DNA analysis and genealogy. There is a surprise for Dec as he finds out he has close family he never knew existed, while Ant's history takes him to the United Nations. After a whirlwind tour of the US, it's back to Ireland to investigate a family secret that Ant's family has been trying to unlock for years.

Anthony McPartlin and Declan Donnelly may think they know who they are, but in this two-part documentary, the popular presenters uncover their surprising and emotional family histories, using a combination of DNA and genealogy. The shock revelations include military men in both of their families - one a medal-winning war hero, the other a deserter. And as well as delving into the past, Ant and Dec also get to meet DNA relatives they never knew existed.