I can understand the frustration. On GW2, my boyfriend had an account that was 3 years old, and when we decided to recently start playing it together, he decided to make a new one because he couldn't get into his existing one. Later, after he'd paid loads of RL on the new account, he managed to get into his old account. Unfortunately, GW2 (like SWTOR) does not have the technology to 'merge'/transfer characters from one account to another. The only game I know that offers that is WoW, (although I believe this started people selling characters for real money, etc). Again, I do understand why you're frustrated at this.
There is no way to fix it. SWTOR does not have the technology for that, even if they wanted to do it for you right now. I doubt that they will ever have character account transfer because it opens up the possibility of people selling characters for real money like gold sellers, which are already a problem. I'm very sure they will never bring this feature out, sorry, because I believe it will create too many problems.
Unfortunately, you are going to have to recreate those characters. However, if you are a subscriber and when KOTFE hits, all subscribers will receive a free level 60 creator - meaning that you could recreate one of your toons on the new account. If you wish to recreate more, you will be able to purchase additional 'level 60 creators' off the cartel market (although we have no idea what the cost will be yet). I believe they might come with crafting skills already levelled to a certain point (no idea if you can choose them or if they're given, depending on your class).
You could wait until KOTFE (2 weeks yesterday for early access) and create instant 60s of the characters on the other account (delete the existing character so you can use the name, same class, same looks, etc). They already come with gear, so don't worry about that, and KOTFE will make previous top-level PVE gear ratings obsolete, anyway. You will lose your legacy items and any items bound to those characters. You would, however, be able to mail gold and non-bound items from your old characters to your new ones. It's not ideal, but it will stop you having to go from 1-60 on each character, and will hopefully come with already levelled crafting skills, so you won't have to do that either. I think that's going to be the closest thing to what you're after. It's that or create levels 1s, I'm afraid. :/
Alternatively, kick your brother off your account and make him create new toons. I guess it depends who was paying for the subscription and who initially created the account. I hope this helps you a bit. I would suggest remaking your high level/favourite toons as instant 60s.
