The Newhouse family is selling most of its stake in Warner Bros. Discovery, effectively winding down a partnership that has spanned decades.

The family, which owns the magazine publishing giant Cond Nast, sizable stakes in Charter Communications and Reddit, as well as businesses like Ironman and TurnItIn, revealed in a securities filing Tuesday that it well sell 100 million shares in the company in a block sale for $10.97 each via its Advance holding company, worth about $1.1 billion.

The Sale is intended to provide financial flexibility to support the Reporting Persons ongoing estate planning, its investment program, and for other general corporate purposes, the filing says. WBD stock closed Monday at a six month high of $11.46 per share. The block sale was made on June 30, and following the deal the Newhouses still own more than 98 million shares in the company. That said, the sale puts the family under the 5 percent SEC reporting threshold, which means that it will no longer need to publicly disclose its holdings, giving it the flexibility to sell when it wants without heightened regulatory scrutiny.

The Newhouse family were early investors in Discovery Communications, and when Discovery linked up with WarnerMedia they emerged from that deal as the largest shareholders in the combined company, holding a more than 8 percent stake. The family also had two WBD board members in Steven Newhouse and Steve Miron, however they stepped down from their roles with the company last year after receiving inquiries from the U.S. Department of Justice about a Clayton Act investigation.

The sale by the Newhouse family comes at a critical moment for WBD, which is in the process of splitting itself in two. HBO, HBO Max and the Warner Bros. film and TV studios will form a new studios and streaming business to be led by CEO David Zaslav, with the legacy WarnerMedia and Discovery cable channels forming a global networks business to be led by Gunnar Weidenfels.

Current WBD shareholders (presumably including the Newhouses) would receive equity in both companies after the split takes effect next year.