In a Park Avenue building completed in 1927, two adjoining four-bedroom units on the eighth floor were combined last quarter. The buyer — a 48-year-old hedge fund principal — paid US$ 38 million to merge them. The unusual part is not the price. It is the floor plan that emerged: a single 8,400-square-foot residence with two distinct entrances, two kitchens, and a soundproofed corridor connecting a primary suite to a self-contained two-bedroom wing. That wing has its own laundry, its own service entrance, and its own thermostat. It belongs to his parents.

This is not a renovation curiosity. It is the most visible expression of a structural shift redefining how the wealthiest Americans buy real estate in 2026.

According to the Luxury Outlook 2026 report from Sotheby's International Realty, nearly one in five luxury home purchases in the US is now made by buyers who plan to live with relatives beyond their immediate family — including grandparents, adult children, and in-laws. In Manhattan and Miami specifically, demand for adjoining apartments that can be combined into multigenerational layouts has reshaped the brokerage conversation. The Knight Frank Wealth Report 2026 adds the demographic backdrop: the global UHNWI population reached 713,626 this year, with 162,191 individuals crossing the US$ 30 million threshold since 2021. The buyer pool is not just larger. It is older, more international, and increasingly cross-generational.

The US context: a market reshaping its top tier

The US luxury market entered 2026 in a state of uneven equilibrium. Coldwell Banker Global Luxury's Trend Report 2026 confirms that homes priced at US$ 10 million and above have outperformed the broader housing market for seven consecutive quarters, even as median prices in much of the country have stagnated. The strongest gains are concentrated in four cities: New York, Miami, Los Angeles, and Aspen.

The headline transactions tell the story. A West Village penthouse sold in February for US$ 87.5 million, set to close in 2027 once construction wraps — a record for Lower Manhattan. In Miami-Dade, 42% of condo sales in Q1 2026 went to non-US buyers, with single-family home prices stabilizing around US$ 640,000 and condos averaging US$ 420,000. Aspen continues to operate in its own gravitational field, with five trophy properties trading above US$ 50 million in the past twelve months.

But underneath the headline numbers, a quieter pattern is emerging. The product itself is changing. The buyer who used to want a two-bedroom pied-à-terre is now requesting a three-bedroom plus a separate guest suite. The buyer who used to want a 6,000-square-foot penthouse is now asking whether the unit next door is on the market.

Why adjoining units became the most-asked-for inventory

Three forces converged. First, demographic: Millennials and Gen Xers — the largest cohort of luxury buyers active in 2026 — are simultaneously raising young children and supporting aging parents. The Pew Research Center calls them the Sandwich Generation. The 2026 luxury buyer is one of them. Second, financial: a multigenerational household pools capital, splits maintenance burden, and preserves intergenerational wealth without the friction of a separate property. Third, post-pandemic: the lockdown years recalibrated what proximity to family is worth. That recalibration did not reverse.

The wealth and demand drivers behind the shift

The Knight Frank Wealth Report 2026 highlights a corollary trend that explains why this is not a fleeting cycle. Among respondents earning more than US$ 1 million annually, the spending category that grew fastest since 2024 was not art, watches, or travel. It was health and longevity experiences. The same buyers buying adjoining apartments to house their parents are also buying homes designed to extend their parents' active years.

This is where the design implications become significant. The multigenerational unit is not just larger. It is structurally different. It needs:

Two or more separable HVAC zones with independent controls
Dual primary suites with full bathroom suites at opposite ends of the floor plate
Acoustic separation engineered for two distinct sleep schedules
A second kitchen or full prep pantry, not a secondary kitchen
At least one accessible-design entrance and en-suite bathroom for aging-in-place
A shared central space large enough to host three generations during holidays

Most luxury inventory currently on market does not meet these criteria. The product was designed for a different buyer.

Foreign capital and the multigenerational thesis

The Miami data point — 42% of Q1 condo sales to non-US buyers — is not unrelated. Latin American, European, and Middle Eastern UHNWIs have always purchased multigenerationally. They have been buying buildings, not units, for decades. What changed is that the US-born luxury buyer has converged on the same logic. The cultural import is now the cultural baseline.

The central thesis: luxury is consolidating, not fragmenting

For thirty years, the trend in residential luxury moved toward fragmentation: smaller households, more pied-à-terres, more secondary residences, more curated solitude. The 2026 data reverses that arc. The wealthy are buying fewer, larger, more functional homes — and engineering them to serve more people across more life stages.

The defining luxury asset of 2026 is not the penthouse. It is the penthouse that can hold three generations without anyone feeling like a guest.

This consolidation has consequences for developers, brokers, and brands operating in the space. A 5,000-square-foot single-floor layout designed for a couple with one child is now functionally obsolete in the ultra-prime tier. A 9,000-square-foot layout with two primary suites, two kitchens, three living zones, and aging-in-place features at one end is what the market is paying a premium for.

The Sotheby's report puts it cleanly: this trend goes beyond renovations. It is shaping what architects and developers create from the ground up. Buildings designed in 2024 with single-bedroom premium tiers are already being repositioned for combination sales before they finish construction.

The branded residence response

Branded residences — the fastest-growing category in global luxury, expanding 19% annually per Savills — are responding fast. The Aman Bay Harbor Islands project in Miami is selling adjoining units with pre-engineered combination plans. The Mandarin Oriental Residences in Beverly Hills offers a family floor concept where the entire level can be purchased and reconfigured. Four Seasons Private Residences New York at 30 Park Place added a second primary-suite option to its tower-floor inventory in Q4 2025 after broker feedback. The product is moving fast.

Practical implications for developers, designers, and brokers

Five concrete actions separate operators leading this shift from those reacting to it:

Engineer combination plans before pre-construction marketing begins. Show buyers how two adjoining units can become one without speculative sketches. The plan should be approved by the structural engineer of record and reflected in the offering plan.
Design dual primary suites into trophy floor plates from day one. Retrofitting acoustic separation and HVAC zoning post-purchase costs three times what it costs to build in.
Integrate aging-in-place features without making them visible. Reinforced bathroom walls, wider door clearances, level transitions at thresholds, and lever-style hardware can all be specified without compromising aesthetic. Visible accessibility kills luxury perception.
Train the brokerage team to sell multigenerational, not square footage. The pitch is no longer 5,000 square feet of finished space. It is a floor plan that holds your parents, your kids, and your office without anyone losing privacy.
Document the multigenerational scenario in the marketing materials. Renderings of empty rooms do not tell this story. Renderings of a Sunday dinner where three generations occupy distinct zones of the same floor plan do.

Where this is going

The multigenerational thesis is structural, not cyclical. The Sandwich Generation demographic peaks around 2030. The UHNWI population continues to grow at roughly 32,000 new individuals per year globally. Aging-in-place demand will compound, not fade. Developers planning trophy projects for delivery in 2028 and 2029 are already redesigning their unit mix.

The opportunity for brands and developers operating in this space is to lead the conversation rather than respond to it. That requires creative direction, naming, narrative, and visual systems that signal multigenerational thinking from the first touchpoint — not as a feature in the spec sheet, but as the organizing premise of the project. TBO's architectural visualization and branding services are built around this kind of upstream creative strategy, where the brand and the product converge before construction starts.

For more on how the global luxury market is recalibrating, see our recent coverage on branded residences and the new capitals of luxury real estate.

Closing

For a generation, luxury real estate sold solitude. The current generation is buying proximity — but proximity engineered, zoned, and acoustically separated to feel like solitude when needed. The penthouse of 2026 has two front doors. The grandparents are home. So is the eight-year-old. So is the principal. None of them sees the others unless they choose to.

The next decade of trophy real estate will be defined by the developers who understood, in 2026, that the floor plan is the brand.

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