Explanation of the Assassins Creed story-line up to Brotherhood?

Long story short, I ended up getting Assassins Creed: Brotherhood and Revelations, but I do not have the first two in the series. I would like to play the whole series, but I do not want to commit the time or money into doing so. Could some r/gaming bros help me out and give me a run-down of the plot of the the first two games? It would be much appreciated. Just something quick and simple so that I can understand what is going on. Thanks in advance!