Yes, adult children are qualified to buy life insurance on their parents since there is an insurable interest between children and their parents.
In addition, there are life insurance carriers that offer life insurance for people over 75.
Poeple over 75 may qualify for whole life insurance or term life insurance. And, there's even guaranteed issue life insurance for seniors age 85 and under which means your parent cannot be turned down due to any health problems.
Here's how to buy life insurance on parents over 75