Your parents will have to participate in the underwriting and application process and you will have to show what you stand to lose financially if something happens to them, this is called having an insurable interest in the person(s) you want to insure for life insurance.
If you rely on your parents financially for living expenses, then a term life insurance policy to replace the income they provide to you may be an idea to consider.
If you are worried about their final expenses to cover the cost of their burial and funeral, and you don't anticipate that either you or them will be able to afford them then a permanent life insurance policy can provide lifetime life insurance coverage for your parents.
Here's how you can compare the benefits of term life insurance vs. permanent life insurance.