With their consent and permission, if they're young enough, and healthy enough, and you have the money, yes you can buy burial insurance on your grandparents.
Your grandparents may need to sign the application for coverage. Also, they may have to answer some health questions.
If you are paying for the burial insurance policies you will be the owner and want to name yourself as the beneficiary on their burial life insurance plans.
Since you are their grandchild, you have an insurable interest in them, and can buy life insurance or burial coverage on them.
Several life insurers offer simplified life insurance plans to help pay for burial expenses, including Colonial penn, Mutual of Omaha, and Globe Life Insurance, among others. Here's how you can learn more about burial insurance for your grandparents and get a free quote online.