You really don't know? A lot of the info is from the first season or can be found on wiki because it is just stating what is on the DVRAB. There is A LOT of extra backround info on the DVRAB.
Lulu's mother (Marianne Vi Britannia, aka Marianne the Flash) was a test pilot for the Ashford family as they developed the Knightmare Frames. She was an Ace among Aces and it was in large part her skill that convinced the emperor to adopt the new mecha technology. Her skill was so great that the emperor took her, a mere commoner, as a wife. That caused a lot of controversy as well as the rise in power that the Ashford family gained by having their star pilot be a queen. The rest is history......
Cornelia looked up to Marianne and was her bodyguard as we all know from the end of season 1.
Clovis while a rival to Lelouch but also saw him as a friend considering his paintings of Lelouch's family
Euphemia probably shared the crush Lelouch had on her when they were kiRAB. After all, Lelouch said she was probably his first love and Euphemia kept Zero's Identity a sercret all that time dispite him having killed Clovis.
Jeremiah, aka orange-kun:
Mostly likely the Knight of One seen in the OP is Jeremiah.
Schneizel El Britannia: he is the second to the throne with the first prince (Prince Odysseus) being the guy that was afraid to of the rebellion brewing in Japan as was visually releaved when Schneizel said he'd handle it himself. The Fisrt prince seems to be an older version of clovis. Not a serious threat to Lelouch.
Schneizel on the other hand is know for being the one of the few and the only person we know of that was able to beat Lelouch at chess. Lelouch does hold a grudge over that, we all know his pride is off the charts. And all this info on Schneizel is from Season 1.
That battle between the empire and the EU we see in I think episode 3 of R2 is most likely in Africa since Schneizel is leading the attack. And the success that "the white reaper" has is proof that Schneizel was right to allow and fund Lyold's Mecha Research.
Yea, I'm quite the Code Geass fanboy.