Many fans (including me) assumed that the protagonists of Assassin's Creed I and II were related, since they are both Desmond's ancestors. The writer behind this fall's Assassin's Creed: Revelations has confirmed that's not correct.

Speaking to Kotaku, script writer Darby McDevitt revealed that Altaïr and Ezio don't share a family link. How is that possible, since Desmond can access both of their memories? They could be from separate family trees that eventually converge and produce Desmond, but the two characters don't share any ancestors themselves.

This may or may not be significant to the overall plot of the series, but it's always interesting to learn something new about your favorite video game characters.

Source: Kotaku