Duperreault says of Weill's appointment, “Sandy Weill is an icon in the financial-services sector; someone who has been at the forefront of change throughout his career. Under his leadership, and with our forward-thinking management team, I have no doubt that our goal of establishing a leading insurance and reinsurance business will be realized. It's an honor to serve with Sandy.”

Weill says, “I think it is rare to have an opportunity to be involved with people who have an exemplary record in what is necessary to run a successful insurance company. Brian Duperreault has run businesses very successfully in all parts of the insurance industry from Marsh & McLennan, to the ACE Group in Bermuda, as well as his long stint at AIG.

“Brian's teaming up with Two Sigma marries insurance expertise with an outstanding record of investment expertise, a combination that I believe will work well together, and I look forward to working with the board on the opportunities and challenges that lie ahead.”

According to an Academy of Achievement biography, Weill created Citigroup through the 1998 merger of Citicorp and Travelers Group. The deal faced a legal obstacle: the 1933 Glass Steagall Act, which prevented commercial banks from getting involved in investment banking.

A July 2012 CNN Money article states that Weill helped lobby in 1999 for the repeal of the act.

But the article notes that Weill, who stepped aside as Citigroup's CEO in 2003 and retired as chairman in 2006, told CNBC in 2012 that he believed a firewall between commercial and investment banks is needed.

“What we should probably do is go and split up investment banking from banking,” Weill told CNBC. “Have banks do something that's not going to risk the taxpayer dollars; that's not too big to fail.”