This has to be one of the questions we get the most.
The answer is simple, if you can show insurable interest to the insurance company, you can get a policy on your mother or father, or both.
Being that you are the son or daughter, showing insurable interest is pretty much a given. The death of either of your parents can be shown to be a financial burden on you.
Furthermore, you may need the life insurance proceeds to pay estate taxes or any other financial burden left by your parents.
Adult children are usually a bit hesitant talking to their parents about such a delicate subject, but the longer you wait, the more money will cost you to insure them. Just make sure to explain what the money will be used for, and your mother and father will, most likely, be okay with a policy taken out on them.
You may be asking yourself if it is still possible to insure them because they are 70+, but if they are in good health and don't have any vices detrimental to a person's health - smoking and/or heavy drinking -, life insurance coverage is still possible.