Well let´s put it like this, when you are 60years old, he will be 84years old. When you are 65 years old, he will be nearly 90,years old.....are you getting the picture.
Now, no big deal, but later....................he has a Pension and he wants you to be included, the Insurance Company will say "You are OK, but not her"
He dies, how will you survive financially?
It can work................but usually hot.