Archive · 28 Aug 2026
Two Sigma Founders Escalate Feud Into New Arbitrations
Two Sigma is a large investment company started by David Siegel and John Overdeck.
The two founders have disagreed about how the company should be managed.
Now, two more disagreements are being sent to arbitrators, who act like private judges.
One dispute involves how Overdeck handled a former employee’s pay complaint.
Siegel’s family says Overdeck had conflicts of interest, but Overdeck and Carter Lyons have not yet responded to those claims.
The other dispute concerns whether Seth Platt should become a co-chief executive.
The founders have been arguing for years, and some employees and investors have left.
The company says the disputes are between the founders and do not make claims against Two Sigma’s funds or investment vehicles.
Two Sigma disclosed two new arbitration disputes involving billionaire co-founders David Siegel and John Overdeck.
Siegel’s family alleges Overdeck had undisclosed conflicts while handling a former employee’s deferred-compensation complaint.
A separate arbitration will determine whether Seth Platt automatically becomes co-CEO alongside Carter Lyons.
The founders’ conflict has contributed to leadership changes, senior staff departures and investor departures, according to the report.
Two Sigma said the proceedings do not assert claims against the firm, its funds or investment vehicles, and will take time to resolve.
- Who
- Two Sigma co-founders David Siegel and John Overdeck, along with executives Carter Lyons and Seth Platt, are involved in the disputes.
- What
- Two new arbitration proceedings concern an alleged mishandling of a former employee’s compensation complaint and a dispute over Two Sigma’s management.
- When
- The first dispute was sent to arbitration on August 17, and Platt filed the second arbitration demand on August 18; the investor memo was dated August 21.
- Where
- The disputes concern Two Sigma Investments, a quantitative investment firm; the articles do not specify an arbitration location.
- Why
- The arbitrations were initiated to resolve allegations about fiduciary duties and an unresolved question over the firm’s co-CEO structure.
Siegel’s Position
Overdeck’s Position
Handling of former employee’s claims
Siegel’s Position
Siegel’s family entities allege that Overdeck had undisclosed professional and financial conflicts and that Carter Lyons did not authorize counterclaims against the former employee.
Overdeck’s Position
The claims have been sent to arbitration, but the article says Overdeck and Lyons had not yet responded.
Two Sigma’s management structure
Siegel’s Position
Siegel replaced his former management-committee appointee, Scott Hoffman, with Seth Platt, whose status as co-CEO is being challenged or disputed.
Overdeck’s Position
Overdeck’s side selected Carter Lyons as co-CEO, and the question of whether Platt automatically joins Lyons in that role remains unresolved.
John Overdeck’s divorce case
Siegel’s Position
Laura Overdeck argues that 35% of John Overdeck’s Two Sigma stake, which she values at about $6.2 billion, should be recognized in the divorce proceedings.
Overdeck’s Position
John Overdeck’s lawyers argue that the stake is not a marital asset because Two Sigma was founded nearly two years before the couple married.
- Company
- Two Sigma Investments
- Reported assets
- About $80 billion
- Founders
- David Siegel and John Overdeck
- First arbitration
- Siegel’s family entities allege Overdeck mishandled a former employee’s deferred-compensation claims and had undisclosed conflicts.
- Management arbitration
- Seth Platt filed a demand over whether his appointment to the management committee made him co-CEO alongside Carter Lyons.
- Company position
- Two Sigma said the proceedings do not assert claims against the firm, any fund or any investment vehicle.
- Related divorce dispute
- Laura Overdeck is seeking 35% of John Overdeck’s stake, which she says is worth about $6.2 billion; his lawyers dispute that the stake is a marital asset.