The Elghanayan brothers, who founded Rockrose Development 39 years ago and decided to part ways this summer, have settled on how to divide their assets.

H. Henry Elghanayan will operate under the Rockrose Development Corp. banner, but from new digs at 666 Fifth Ave. His brothers, Kamran “Thomas” and Frederick Elghanayan, have formed TF Cornerstone and will remain in the former Rockrose offices at 290 Park Avenue South.

Henry will operate about 2,600 apartment units, including those at 666 Greenwich St., 100 Jane St., 410 W. 53rd St., 22 and 41 River Terrace, and the East Coast in Long Island City. He will also develop three more of the LIC Pepsi sites and a parcel that can host a 1 million- foot building near the Javits Center.

TF Cornerstone has more than a dozen Manhattan buildings, including 45 Wall St., 99 John St., 201-203 E. 69th St., 77 Bleecker St., and two properties in Long Island City.

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The General Motors Building at 767 Fifth Ave. will for now remain the General Motors Building, with the car maker as its tenant.

According to the New York Observer, GM has essentially signed a new lease at the Boston Properties-owned tower for 114,300 feet covering the 14th through 16th floors. The 10-year lease with renewal options to 20 years also includes a work letter, which means GM will be renovating, sources told The Post.

GM was supposed to start a new lease at another Boston Properties building, 601 Lexington Ave., formerly known as the Citicorp Center. But after filing for bankruptcy the car company rejected the lease. It was worth about $110 a foot, sources said.

The new lease was for much less and includes a clause that prevents the building from being renamed after another car maker, should one rent there.

A Jones Lang LaSalle team of Peter Riguardi, Michael Shenot and Lloyd Desatnick repped GM.

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The Gateway Center has officially opened in the Bronx.

The nearly 1 million-square-foot, LEED Silver retail mall is 90 percent leased and 80 percent open. The mix of retail and restaurants includes BJ’s first wholesale club in the Bronx, Bed Bath and Beyond, Toys “R” Us/Babies “R” Us, Best Buy, Target, Marshall’s, Raymour & Flanigan, Staples, AT&T, T-Mobile, Payless ShoeSource, and Applebee’s.

The stores are doing well, especially in the evening, and some are staying open as late as 11 p.m., said Glenn Goldstein, president of developer Related Retail.

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Decorator Liz O’Brien, whose gallery specializes in 20th Century decorative arts furniture, lighting, jewelry, carpets and textiles, is moving from Fifth Avenue to First. O’Brien is relocating to a 2,400-foot shop at the Interior Design Building at 306 E. 61st St. The store was vacated by Historical Design, which consolidated into its loft warehouse.

O’Brien is joining interior designer Bunny Williams and her husband, John Rosselli; Amy Perlin; Sentimento and other destination tenants, said Philip Carter, who owns the building with Alan Schwartz, under the Urban Partners name.

The deal was negoti ated directly with O’Brien. CoStar lists the asking rent at $135 a foot.

“These are all destination tenants,” Carter said.

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