Did the Frye family have a case of Incest

In AC Syndicate we play as both Jacob and Evie Frye. But since the animus allows to relive the memories of only one's ancestors, the ability to relive the life of both Evie and Jacob, indicates that they are both the ancestors of the same person.

What is the explanation of being able to play both twins?

Solution 1:

The animus has evolved since the days of Assassin's Creed 3, with Desmond and his ancestors. Essentially, Abstergo has turned the Animus into an entertainment product by Assassin's Creed Unity, with the ability to pretty much follow any person regardless of genetic history. Assassin's Creed Unity and Assassin's Creed Syndicate as such are not based on the genetic memory of the person in the animus, but rather recordings of genetic memory obtained by Abstergo, poured into the mold of an action game designed for modern consoles. It's essentially a form of propaganda by the Templars.