They don't have to be on his Chase accounts. If his other lenders report to TU and EX. It's easy for them to pull up and look for patterns. Especially if those lenders report in detail. The current balance, minimum payment needed, actual payment and remaining balance.
His total exposure across 5 cards was only $12K ($500 more than mine across 3 cards) and more than likely those were going to be his limits and long as he had those cards b/c CLIs are very rare with Chase---so I say good riddance. If his total exposure was say $60K or more with those 5 cards that would be a different story IMO. That's 5 more slots he can fill in due time with better lenders who WILL possibly give him better CLs.
BUSINESS 
They seem to like people like my mother and my sister. "Real" people. A couple of majors, a couple of store cards, occasionally something kind of dedicated, like the Amex/Visa/MC for a warehouse store, and maybe a gas card. They pay their balances when they get their bills, and seldom carry a balance. Chase is rumored to like their card/s to be near the front of the wallet. They like relationships.
Like good BBQ, low and slow.
To the OP: I have more new accounts than I think they'd really like, but that includes AUs - not sure how they count that. FWIW, I'm working with an income 3x your brother's, with total outstanding debt 1/10 of his, and number of cards 1/4 of his (again, depending on how you count AUs - could be fewer).
It may be worth making an appointment at a branch and talking to a human, face-to-face, and ask if they'd help you guys create an action plan for getting back in their good graces.
@bourgogne wrote:
@Anonymous wrote:
What do you mean by Chase likes clean and doesn't like games?25 cards is a game, plain and simple. 16/56 debt to income. everything in credit is risk. you know all this, I think we all do. not judging but collecting cards or credit limits seem a bit boring to me vs getting some actual utility out of the situation. again just my .02.
You say that the OP's brother was playing a game by having 25 credit cards, and that it's boring, and that he wasn't getting utility out of the cards... but you're not judging?
Sorry to hear this happened OP. Through mergers Chase ended up with several of my CC, with balances, from other banks. I think I had four in Chase at one time. They closed one, I closed one in 2014, and that left me with two. I carefully got Marriott and Hyatt in Dec 2014, Jan 2015 but I was leery and havent asked for anything since. The proximate cause of my AA was high balances.
Hopefully the Freedom can be salvaged, and longer term your brother is able to get something useful.
AA is not the end of the world, but it is nerve wracking until you go a few months past it. 
