You can have many separate accounts as retailer. But if you as individual are the registered entity on two separate account and hold long futures positions (US exchange traded) in one account and short positions of the identical contract in another of your account you will get a broker message to tell you to stop doing this shit if you are L-U-C-K-Y, else your account might get frozen and you will have a few questions to answer...is this clearer now? you can look it up, I won't do your homework...
M.W. = AsiaProp ... volpunter... DiceAreCast. Not originally Canadian. Probably German, spent 10 of the last 12 years in Hong Kong, now living on Vancouver Island north of Victoria.
https://ibkr.info/node/593 Besides ever heard of having accounts with 2 different brokers, huh? Under the same name. Find something else to be angry about.
Futures, in particular, do not want you to be long and short in different accounts. There was a guy recently who was fined because he "moved money" between accounts by being long and short futures across multiple accounts. I wish I could find the link...