Just to chime in with my 2¢... usually there's no harm in asking for something, since generally the worst they can do is say no, right?
In this case, though, there is more they can do - if they believe there's a chance they won't get paid back, they can close your account.
Since your non-Citi accounts are showing as delinquent on your credit reports, Citi already knows there's a problem - the lates on the other accounts are likely what got their attention, not so much your carrying a high balance alone.
If you call them about reinstating your previous limit, they will likely ask you about the accounts you are currently late with, and if they do you'll either have to be truthful and tell them you're unemployed, or you'll have to lie. Neither of these is a good option, IMO.
If it were me, I would just hang on for the time being. Once things are back on track then go about getting your limits reinstated. I went through a similar thing with my Synchrony accounts years ago (Synchrony is notorious about CLD when you are late with other lenders), and eventually my credit limits did bounce back.
As for your accounts impacting your brother, you can avoid that by having him removed as AU from the accounts (like others have already mentioned) or he can simply 'ride out' the situation with you. If you do decide it's best to remove him, if you can't do it online and must call, I would not mention the credit line issue... again, I would leave that alone for the moment. Also as has been mentioned, once you have him removed he'll likely have to dispute the entries with the three credit bureaus to have the accounts removed from his own reports in a timely manner. Ideally it should happen automatically - and eventually it might - but in my personal experience it can take a while without the disputes (YMMV).
Good luck!
