Jeremy was Executive Assistant to Charles Hoskinson (self-appointed "CEO" of Ethereum) between December 2013 and September 2014. Charles was ejected from Ethereum at the "Red Wedding" in June 2014, but it appears that Jeremy hung around for a few more months, through to September of that year, according to his LinkedIn profile.
Charles and Jeremy later collaborated as co-founders of IOHK (later partially rebranded as IO Global) in April 2015, a company most famous for the development of the Cardano blockchain.