Neat thread, Dan.
My two brothers are fairly close to me in age: one is 3 years younger, while the other is 2 and a half years older.
We used to play games together like crazy, and my dad was way into it too. The Commodore, NES, and hours and hours and hours and hours and hours of playing GameBoy in the car with link cables. Tetris. Pokemon!
More recently, the DS was like a revitalization of our GameBoy days. Mario Kart! Hell, Mario Party! And we would enjoy the hell out of New SMB on the Wii, of course. That game breaks relationships, divorces family, etc. Unfortunately, my older brother has since realized that he can't stand me anymore, so we don't talk... (Pretty literally. He actually said that his birthday present to me was voluntarily saying "hi" to me.) That kind of kills our gaming. He's mostly gone into PC gaming now anyway, I guess, although Skyward Sword brought him out for a while. I think he's into Guildwars or something.
My younger brother will still play games with me, although I think he thinks it's uncool because of how much I suck at anything that requires dual control/is first person or uses anything novel that came out after the N64.
~ He's also mostly stuck in his room playing PC games, or games on his PC.