http://kwennnet.tripod.com/kwennsgallery/id17.html
I think this is all we know.
Lucas also used to have it in the ROTJ script that Owen and OB1 were brothers, so unless its actually been in a movie it doesn't matter. I'm not saying that choking is a Skywalker only thing but maybe its a weapon so powerful that only the choosen one can do it, then his son has his genes so naturally he can do it too. I just don't think its a coincidence that only Skywalkers have done the force choke. Hopefully the first time Anakin uses it, it comes as to a complete shock and they have no idea how to defend it.