I think a lot of times sibling #2 tends to "hide" what they know. Maybe to steer away from what the older sibling does, find their own way. I am sure she knows a lot more than she is letting on......

Ds2 is obsessed with "Rock n Learn Sight Words" DVD's at the moment. He has watched the one DVD once a day for about a week and now knows all the 60 some sight words included. He walks around everywhere we are, finding the words and gladly yells them out for everyone to hear...:-)
I have to say I really enjoy them too. Some catchy melodies on there.

"Reading Eggs" is also something that he asks for periodically. And "Starfall" as well.