[PirateEggs]

In the first one they need info from your ancestor(s).
It's hard to explain without giving out any spoilers. If you're going to play AC III, make sure you have played all the others, and in the right order, or you will get extremely lost.

I started playing AC II when I was ~75% into the first one, and I was still missing information, so I went back and finished the first one before continuing.
I have only finished the first one, 60% in AC II, and probably 10% in Brotherhood.