Assuming you are asking if you, as an adult child, can buy travel insurance for your elderly parents - the answer is generally yes!
Most travel insurance policies have no age limit, although some policies may exclude coverage for pre-existing medical conditions for travelers over a certain age (usually 75 or 80). So as long as your parents are otherwise healthy, they should be able to get travel insurance.
Of course, each insurer is different, so you’ll want to compare a few different policies before you buy. You can use a tool like SquareMouth to compare policies from multiple insurers side-by-side. Just enter in some basic information about your parents’ trip, and you’ll be able to see which policies will and won’t cover them.