Dallas Mavericks owner Mark Cuban signaled he is about to take a hard look at Reading International, the New York theater owner and real estate developer embroiled in a family dispute.

Cuban, who also stars on ABC’s “Shark Tank,” is an investor with Todd Wagner in Wagner/Cuban and owns the competing Landmark Cinemas, including Sunshine Cinema in New York.

Cuban’s stake in Reading is no longer a passive investment, according to a 13D form he filed Monday with the Securities and Exchange Commission.

Investors who plan to be “active,” or press for changes at a company, file a 13D, while so-called passive investors like mutual funds use another form, known as a 13G.

Cuban holds 207,611 Class B voting shares, or 13.1 percent of Reading’s outstanding voting stock, that he earlier purchased for $1,042,450. He also owns 72,164 Class A nonvoting shares.

His voting power is second only to that held by the estate and trusts of the late James Cotter Sr.

The elder Cotter died in September 2014 after his youngest child, James Jr., was installed as CEO. Since then James Jr. has been ousted by a portion of the board at the behest of his two older sisters.

Reading has approved plans to redevelop its Union Square Theater at Tammany Hall, and has other plans in the works to redevelop Cinema 1, 2 and 3 along Third Avenue opposite Bloomingdale’s.

In New York, Reading also owns the Anjelika Film Center, the Minetta Lane Theater and the Orpheum Theater.

In April, a New York judge allowed the off-Broadway show “Stomp” to go ahead and break its lease at the Orpheum, where it had been for 21 years, due to lack of repairs, although the judge noted that under its license, it could be subject to fines.

James Jr. blamed the outcome on his older sister Margaret’s mismanagement of the theaters. But Margaret and another sister, Ellen, banded together and got the board to remove Cotter Jr. Ellen was appointed interim CEO.

James Jr. is fighting back and has filed other lawsuits against the company.

The company did not return a call for comment.