Single Account play on Multi Platforms

I am inquiring how to play on both the PC and the PS3 at the same time. I have a former future gamer (child) who has now made a character to play in game on my account. I am trying to figure out how to be online while the former future gamer is also online. The future gamer would be on my PS3 and I would be on the PC.

I don't see the logic in having the ability to create so many characters on a single account, but having to have multiple accounts in order to play at the same time on different platforms with different characters.

Please advise.

You can't log into one Service Account more than once at a time, at all. Do you really think SE would allow 8 people to play the game for the price of a single monthly fee?

The 'point' of many characters is that some people like to have variety in gameplay and this game is not at all 'friendly' to some people who want to level different jobs, it becomes a horrible dungeon/FATE grind on second and subsequent ones. Some folks like to play different races, some folks like to re-play content which is only doable once.

There are many reasons why some players create many characters, though I suspect they're in the minority .. I have 4 at the moment. :)