Insurable interest does exist between spouses, parents and children, siblings, family members, and business partners.
In addition, to buy life insurance on another person you will need that person's permission, and the person may need to sign the application, as well as, answer some health questions and perhaps take a physical exam.
There are life insurance companies that do offer life insurance with no exam, depending on how much life insurance you need. If you just need money to cover funeral and burial costs, it may be easier to get coverage than you think.
For instance, Globe Life Insurance offers people age 78 and under up to $30,000 of simplified life insurance without any medical exam needed. You can get a quote and apply online for coverage.