Video Game Addiction Support Group

I don't envy your situation at all. Twelve year old sons have a hard enough time listening to their mothers' descenting opinions, but you're not even his birth mother and have an opinion that is against something he cares very much about. On top of that, a mother who not only enables, but shares his problem.

My only credentials are that I'm a recovering video game addict and I was an addict even as a 12 year old boy (I'm 1 month shy of 28 now).

1) Read about the struggles of video game addicts here and elsewhere. Several legitimate news agencies have articles that have covered the topic of video game addiction.
2) Get on the same page with your partner. You need to reach a consensus on what your expectations are for little 'Jimmy' (I'm just calling him that because it's easier than "12 year old" each time). You need mutually agreed-upon answers for such questions as, "How much time is too much in this house?" "Should he play at all since he gets so much time at his mother's house?" "What is the appropriate punishment for: disobedience, going over time, or throwing a tantrum when the rules are enforced?"
3) Communicate with Jimmy. Share some stories you've read about video game addiction. Make him aware that video games aren't going to help him be a real man, grow-up, be really smart, or whatever it is he ultimately wants. Also, (and you may want his father to do this) be very clear on the new rules that have been established regarding game play. Again, emphasis why. Twelve years olds are not too young to understand such things, and they'll appreciate being treated with such respect.

Get him off the electronic opium as soon as possible. He's at the stage in his life where he can learn the most he'll ever be able to... the piano, a 2nd language, basic etiquette and social skills... if he uses all that valuable brain potency on killing digital Nazis or collecting virtual animals, he'll actually be killing his life's potential and collecting worthless memories.

I know it probably sounds like we're a bunch of freaks. But this is a legitimate issue. I'm apart of the first generation that has been in front of a video games since childhood. 3 of the 6 people in my job are addicted to video games. We're 27, 26, and 32 years old. I've caught up with two of my best friends from different grades that I grew up with (read "same age as me"). I had no idea they were into games until recently. I found out that both are struggling with/have struggled with playing games too much. I am talking about failing college classes, losing girlfriends, and skipping work - kind of too much.

Please do what you can to stop the cycle. If you want him to grow up to be someone who watches TV too much, let him watch as much as he wants now. If you want to see an adult who was once under your care only work to pay the bills and feed his video game habit, by all means, encourage him to sample the full gambit of video games out there. But if you want to see Jimmy be a confident, capable individual who has compassion and can exercise self-control, please get started now.