Two Big Island-based residential real estate brokerage companies are merging in a deal that involves one of the island's top-selling firms.

Windermere Island Properties LLC and C and H Properties Inc. said they will consolidate operations over the next several months, but will maintain existing offices and agents.

Windermere, an affiliate of western U.S. regional operator Windermere Real Estate, opened an office in Kailua, Kona, in 2006 followed by one in Wailea, Maui, last year. The firm has 18 agents and is owned by members of the Knowles family who become co-owners of the merged firm, Windermere/C and H Properties Inc.

C and H Properties was founded in 1981 and is headquartered in Waimea with 15 agents. The company brokered sales of $1.4 billion since 2000, including almost $250 million last year.

The merged firm will continue to operate two project sales offices for new condominiums — Ke Kailani at Mauna Lani Resort and Kauna'oa at Mauna Kea Resort — operated by C and H.

Steve Hurwitz, a C and H cofounder, becomes president of the merged firm. Beth Richardson, Windermere's principal broker, is the principal broker of the new entity.