In some cases, two unrelated individuals went together to purchase a home, and each wanted their own living space. Sometimes, one purchase purchased the home but knew that they needed or were going to be advertising for someone to share the home with them and live in their own secondary master suite.
There have been those single seniors, especially in more recent years, who have employed the "Golden Girls" concept of having one or more mature roommates to share the home (and chores, grocery shopping, friendship, and meals) with them - called "house sharing" among other names for this concept.
Two college-age students, while attending school or immediately afterward may desire to share a home that of them purchases, and this gives each of them equal living space.
There are many additional reasons for having two master suites in a home - two roughly equivalently sizes or even identical bedroom and attached bath areas (en suites). Some people may have visiting relatives on a regular basis. Married children may come with their families for occasional weekends throughout the year. When the owners entertain and their guests want to stay the night, at least one of them can be accommodated in this way. With the national movement of young adults under 35 who have finished college or the military moving back in with their parents (or in some cases never having left), this gives them more separation and adult space away from their parents. Then, there is the case of occasional illness, surgeries, and other forms of stress where the owners of the home may desire their partner to have a separate but equal sleeping area while they are recuperating.
Then, there is the idea that a separate but equal (exactly or roughly) master suite on the opposite end of the house would provide the perfect long-term accommodations for the parent or parents that have been invited to live with their adult children homeowners. This is strategic in two important ways for the homeowners.
First, there is no construction, renovation or remodeling (other than minor decorating like paint, fabrics, furnishings, and accessories to suit the parents' tastes) required to create the additional space. There is nothing required design-wise to create the room and the build it - meaning there also is no cost, construction mess, or delay in occupying the space. This is all the more attractive if it happens to exist on the main floor or it is a single-story home. Otherwise, an elevator may need to be considered if it doesn't already exist.
The bathroom may need to be treated to lessen the slipperiness of the tile floor and to provide safety bars, handheld showers, some type of seating in the shower (fold-down or a permanently created bench), and stronger lighting.
Still, most of the construction work will already have been done. It the best case example, it is move-in ready now.
The second way having a second master suite inside the home that can accommodate aging parents who move in with their adult children homeowners is that it all is contained in one building - no additional construction and no extension into the yard. As much as ADUs (auxiliary or accessory dwelling units) are a good option for housing parents who want to be near their children (or the other way sometimes), they aren't allowed in every locale. Plus, there is the construction, installation of utilities, and other site work that has to be done. It is not ready today as the existing second master suite already is.
A second master suite, if it already exists in the home, can offer many benefits.
Steve Hoffacker, CAPS, CEAC, SHSS, is a licensed Certified Aging In Place Specialist - Master Instructor and best-selling author of aging in place books. To learn about this and other programs for aging in place or universal design, visit stevehoffacker.com or call 561-685-5555. Also, check out the "Aging & Accessibility" groups on Facebook and LinkedIn.