Boston-based Blue Flag Partners has acquired a collection of four guest houses in downtown Nantucket for $25.1 million, with plans to partner with Life House hotel group on the management and restoration of the historic boutique hotel properties.

Brokers say the $25.1 million price is the island’s priciest sale so far this year. It’s more than double the $10.8 million Nantucket-based Center Street ACKquisitions paid in 2005 to acquire the four guest homes, the oldest of which dates to the 1840s. The Gate House, Roberts House, Meeting House and Manor House — together, dubbed The Roberts Collection — are located on India, Chestnut and Center streets on Nantucket and house a combined 58 guest rooms.

Life House, a venture-backed hotel group headquartered in New York, will manage the properties through the summer 2019 season. Blue Flag’s in-house development, branding and construction teams will then undertake a renovation for a spring 2020 season debut. The renovation will include several food and beverage concepts, upgrades to guest rooms and common areas, and revamped lobbies and indoor/outdoor public spaces.

“As Nantucket locals, we are honored for the opportunity to steward a prominent historic property like The Roberts Collection in the heart of downtown,” said Terry Sanford, Blue Flag’s co-founder, in a statement. “We’ve found a perfect partner in Life House as we plan to pay homage to the property and the island’s roots while re-imagining the experience for guests and neighbors in a capacity that is both familiar and refreshing.”

Rami Zeidan, founder and CEO of Life House, said the Nantucket project would be the “first of many” in New England. Zeidan and Yury Yakubchyk founded Life House in January 2017, and the startup has since raised $40 million in early stage venture funding, according to Crunchbase.

“We’re actively seeking opportunities to acquire, brand and operate other hotels in primary and secondary urban and resort markets throughout the region,” Zeidan said in a statement.

Jason S. Weissman, Nicholas M. Herz and Kevin Benzinger of Boston Realty Advisors represented Center Street ACKquisitions in the sale.

“The Nantucket Portfolio is an irreplaceable hospitality asset that delivers a genuine Nantucket experience,” Weissman said in a statement.  “Center Street ACKquisitions did a phenomenal job at preserving the ethos of the vintage properties, while adding value to the entire portfolio throughout its ownership.”

Timothy D. White, manager of Center Street ACKquisitions, said in a statement that Boston Realty Advisors garnered “global attention” for the sale.

“The hospitality sector is a complex asset class,” White’s statement said. “When that complication is compounded with a property in a unique, seasonal location, we knew that we needed a capital markets team with extensive experience in boutique hotels, complemented by a proven track record in Nantucket.”