I did find earlier articles saying that JP Morgan would be developing on ethereum from some more reputable sources dating from October:
http://www.businessinsider.com/jpmorgan-is-developing-a-new-blockchain-project-2016-10
But guess who they cite? Yup, Coindesk. They also cite the WSJ, but that is behind a paywall so I can't confirm any of their info
And there is nothing to back up this recent article, nor anything to confirm that Santander is now involved, nor even any evidence that JP Morgan is following through with their plans from October, which was poorly sourced as is.
This one article is not enough for anyone to take this seriously, and looking through other coindesk articles I can see that they rarely ever cite their sources, this whole thing reeks.
Two sources I've found that talk about earlier bank lead blockchain projects
http://www.huffingtonpost.com/david-seaman/ubs-santander-announce-bl_b_11683838.html - "Mr. Whelan explained that even though the project uses Ethereum technology, it is not exposed to the public Ethereum blockchain. London-based blockchain lab Clearmatics, involved with the settlement coin concept, started with a flavor of Ethereum but this project is likely to end up being rather proprietary in nature." which means that they will likely not use the ethereum blockchain in the end.
http://www.reuters.com/article/us-banks-blockchain-ubs-idUSKCN10Z147 The most reliable source I've found writing on this, doesn't even so much as mention ethereum.
Until we see official word from either Santander or JP Morgan on this, this should be treated as false information, and even then it likely wouldn't mean they are involved for any reason beyond research purposes
Nice try-
“Moreover, Enterprise Ethereum will build upon the current Ethereum scaling roadmap and maintain compatibility and interoperability with public Ethereum.”
http://www.coinspeaker.com/2017/02/14/microsoft-jp-morgan-santander-others-form-enterprise-ethereum-alliance/
http://coinwelt.de/2017/02/jp-morgan-und-santander-mitglieder-bei-enterprise-ethereum/
http://www.criptomoedasfacil.com/2017/02/jp-morgan-e-santander-anunciam-criar-nova-corporacao-baseada-no-blockchain-do-ethereum.html
Choose the language you understand
So you post 3 more articles from obscure publishers that don't cite their sources, and that somehow debunks my point? Nothing you just linked holds anymore water than the original Coindesk article.
I see, you don´t want to believe it. But keep an eye at the media, you will get your articles.