https://blog.medicaremadeclear.com/medicare-coverage-for-non-working-spouses/
If Your Non-Working Spouse is Older
Your older spouse may qualify for Medicare on your work record at age 65, even if you’re not getting Social Security or Medicare yourself—but only if you are at least 62 years old. That’s because you qualify for Social Security at age 62. You don’t have to actually file for Social Security benefits in order for your spouse to get Medicare; you just need to be old enough to file if you wanted to.
If your spouse is covered by your employer health insurance, he or she may want to enroll only in premium-free Medicare Part A until you retire or your employer coverage ends. Part B—along with its premium—can be added later without penalty as long as your employer coverage is creditable, which means the benefits have to be at least as good as what Medicare provides.
If your spouse is more than 3 years older than you, then he or she may buy Medicare Part A until you turn 62 and the premium-free benefit kicks in.